One of the trickiest parts of maximising efficiency in a solar installation is dealing with variations in power output among panels and strings of panels in the same system. SolarEdge is a leading company that has developed a unique solution to the problem of irregularity in solar panel array output. It uses a solar system architecture that utilises per-module maximum power point tracking (MPPT) to tackle system efficiency from a holistic design perspective, providing an ingenious balance of system strategy for solar system efficiency and energy savings.

Centralised MPPT inverters 

In order to explain the innovative inverter technology that SolarEdge specialises in, it is first essential to understand how conventional solar system inverters function.

System losses can sometimes be attributed to the nature of industry-standard crystalline solar panels themselves, which are susceptible to partial shading and overheating, and sometimes attributed to the nature of conventional inverters, which do not perform MPPT for individual modules.

There are many potential reasons for variation amongst panels in an array: natural variance in a solar panel’s rated capacity is typically +/-3% of rated output, shading can happen on some parts of the array but not others, the array can heat up unevenly, and strings of panels on different sides of the same roof can generate different amounts of electricity at different times of day.

In a system with a centralised-MPPT, single-input inverter, total solar system array output will be limited by the panel that is producing the least amount of power–the weakest link is where the chain breaks. If an inverter has only one input for one ‘string’ of panels, you may have to deal with losses on a regular basis, or buy more than one inverter to improve the overall system efficiency.

Some inverters support MPPT at a string level, which does help to minimise losses, but the inverter still cannot ‘see’ into a string to monitor and control what individual panels are doing. This means that your system is not taking full advantage of all the power produced by your panels, which in turn means higher cost per watt of your system and extended payback periods for your solar investment.

An example of partial shading in a conventional multi-string inverter system (Image credit: pvsolarchina.com)

So in summary, the current industry standard multi-input inverter design approach, while much more efficient than inverter systems of the past, still only addresses the efficiency problem on a string level. Even when the inverter itself is functioning efficiently, variance between the panels within the array limits the potential overall system efficiency, and therefore, its usable electricity output.

SolarEdge Solar Power System Architecture: Holistic solar system design using module-level MPPT

The engineers at SolarEdge took a bird’s-eye-view approach to system design. An image on their homepage is telling of their methodical, thoughtful approach: transposed over a photograph of a Zen Buddhist rock garden read the words, “Good design always requires a holistic viewpoint. Take a step back, consider the details from above, and you get a better perspective on how to deal with the problems close up.”

Benefits of SolarEdge technology:

-Up to 25% increase in power output compared to single- and multi-input inverter system arrangements

-Superior inverter efficiency (up to 98%) – peak performance in both mismatched and unshaded conditions

-Flexibility in system design options: SolarEdge system architecture allows parallel uneven length strings, panels of different wattages and from different manufacturers (more inventory options); installation involves fewer components and less wiring, which means faster installation and better roof space utilisation than conventional systems

-Interactive, ‘from anywhere’ monitoring offers a new world of opportunities with regard to system troubleshooting maintenance

-The power optimizer (MPPT tracker) can be embedded into any module as a certified junction box–possible on-site or factory-based integration into solar modules

-Superior safety for installers and firefighters: Electric arc detection and termination features; safe module voltage when disconnected or off

-SolarEdge ‘Inverter Configuration Tool’ software means immediate installation feedback for quick system commissioning

How does SolarEdge distributed smart inverter technology work?

SolarEdge System Architecture Components:

Three components form the balance of system in SolarEdge’s ‘system architecture’.

-Module-embedded power optimisers, which monitor and regulate the power output of all the individual modules in an array, in order to maximise overall system output–these can be installed on-site, or may be pre-assembled in solar module factories of companies that are in a partnership with SolarEdge,

-A smart inverter, which inverts the DC power of all modules to grid compliant AC, and

-A monitoring system, data from which is accessible via the Internet.

SolarEdge System Architecture Features:

Module-level MPPT

The inverter uses a highly-optimised algorithm to keep each module at the same constant MPP, preventing power loss even under panel mismatch or partial shading. In fact, even panels from different manufacturers can be used simultaneously in the same array. (This offers intriguing possibilities for future applications in Building-Integrated Photovoltaics (BIPV); solar windows, solar walls, and rooftop solar arrays could all be routed through one inverter.) The algorithm also allows the system to react more effectively to changes in irradiance and temperature, a big benefit on cloudy days.

Highly Efficient DC Conversion

Each power optimiser performs a DC-DC power conversion (peak 99.5% efficiency) that allows it to boost or buck output voltage of modules in the array to ensure a fixed string voltage.

Fixed String Voltage

The voltage of a string is held constant at the optimal point for DC to AC conversion, regardless of the number of modules in a string, or external factors such as weather or shading. This feature means that there are fewer limits to system design and panel location, greater inverter efficiency and reliability, and lower installation costs.

Advanced Power-Line-Communication

A range of module-by-module status indicators (current, voltage, etc) are continuously measured and communicated by the power optimisers. Data are transferred through the existing DC power lines, meaning that there is no need for extra wiring. For ease in monitoring all the goings-on within the system, the inverter houses a LAN- and wireless-capable communications hub, enabling the owner or operator to view system performance in detail on a remote monitoring server from a computer or other even hand-held devices.

Performance data being recorded on a remote monitoring server also means that the system owner or operator can quickly identify and troubleshoot problems with your system, should any arise, minimising or eliminating the need for site visitations and associated travel charges.

SolarEdge: certifications, awards, and recognition

-ETL Mark: Proof of compliance with North American safety standards

-CE mark: Panel is compliant with European Union regulations

SolarEdge has also  been rewarded for its outside-the-box thinking with numerous awards, including the Climate Change Business Journal’s 2010 Business Achievement Solar Technology Merit Award, and the 2011 Red Herring Global 100 Award, where it was recognised for its achievements in the solar power optimisation field.

About SolarEdge

Founded in 2006, currently engaged in partnership agreements with module manufacturers and integrators in Europe, USA and Japan, which provide SolarEdge technology alongside their current services.

-Company Headquarters-

Hod Hasharon, Israel

Other offices in USA, Germany, and the Asia-Pacific region

Solar Choice is a solar installation comparison service: we don’t undertake our own solar array installations, but we do offer free independent solar quote comparisons of what’s on offer from trusted solar system installers nationally. Our installers may use components from different manufacturers, and if you’re new to solar power installations, you will probably want to know what distinguishes one company’s panels, inverters, batteries, and other system parts from those of their competitors. This article is one of a series written to help you make an informed decision about purchasing your solar power system.

Written by James Martin

Analyst

© 2010 Solar Choice Pty Ltd

Resources and Links:

Solar Edge homepage

Solar Edge: Company Presentation (pdf)

SolarEdge Power Optimiser: Module-embedded solution (pdf)

SolarEdge: Technology overview

The Independent Pricing and Regulatory Tribunal (IPART) has recommended that the price of electricity in NSW increase by between 16.4% and 18.1%. Changes will come into effect from 1 July, 2011.

This would mean that, on average, residential customers will be paying between about $230 and $315 in additional electricity costs per year, with average business customers paying between $325 and $528 more per year.

The increases are generally seen to be a result of rising network costs and the Federal government’s Renewable Energy Target (RET). IPART Chairman Rod Sims attributed 6% of the rises to the RET, 10% to network costs, and the rest to inflation. Chief executive of the Clean Energy Council, Matthew Warren, however, has recently offered the opinion that the rises are not attributable to the RET so much as the NSW feed-in tariff scheme, which he described in a media release as ‘over-ambitious’ and as having created a boom-bust cycle which has in turn created instability in the market for the emerging solar power industry.

According to the Sydney Morning Herald, under the price change proposals, AusGrid (known until recently as Energy Australia) bills will rise 17.9%, Integral Energy by 16.4% and Country Energy by 18.1%. These are the maximum percent increases that power retailers will be allowed to implement.

Australia is home to some of the least expensive electricity in the industrialised world, as has been pointed out by, among others, Ross Garnaut, author of the Garnaut Review.

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Sources and Links:

Sydney Morning Herald, “Huge rises in electricity prices revealed”

Clean Energy Council, “IPART blame game hits wrong target”

We here at Solar Choice are regularly asked about not only technical issues related to solar power, but also about which Installers are the most reputable and dependable. Even before considering these very critical points, there is the important issue of deciding if Solar Electricity is the right investment for your home and energy security. As a way to assist in this process we have formulated and answered 14 key questions for you to consider when deciding whether solar power is right for you.

1 What is your current energy usage?

Prior to going ahead with installing a solar photovoltaic system, it is very important that you are aware of your household’s energy consumption. You should be able to attain this information from your electricity bill, where this number will be shown in the form of œKilowatt-hours (kWh) or alternatively as œUnits. If this information is not stated, then contact your Electricity Retailer, who will be able to provide it to you. Once you are aware of your energy consumption, you can then compare this against the potential yield of a solar system: As a guide, 1kW of PV will generate 4kWh of electricity each day “ but this will vary depending on your location, the position and orientation of the system on your roof, and the seasons. A Solar Choice Broker will be able to assist in sizing a PV system that meets your needs.

2 How quickly do you want to see a return?

Obviously most people will answer, “as fast as reasonably possible”. Most incentives in Australia are net feed-in tariffs, which encourage reducing the amount of energy consumed in order to widen the gap between what you produce and are rewarded for. A standard rate of return on a smaller system (under 5kW)is usually expected to be under 5 years. On a larger system (5-10kW) the expected payback period is around 5-7 years. Although the initial up-front cost is considerably more, the long term benefits of these systems far outweigh those of the smaller systems.

3 How much money are you prepared to invest (spend)?

One objective of investing in a Solar PV system may be to cover your annual bills or to at least reduce them. Some individuals simply want to get the most cost-effective system and keep spending to a minimum whilst still benefiting to some extent from the generous feed-in tariffs. Others may want to maximise available roof space and install as big a system as possible with the goal of generating as much electricity as possible. Your Solar Choice Broker will speak with you about your roof to determine just how many panels will fit. Solar energy conversion technology (photovoltaics or PV) has come a long way, and many are investing for sound financial reasons. Returns of up to 18% are achievable. Whatever your aim, Solar Choice will do their best to help you reach that target.

4 What Government rebates will you receive?

In Australia, there are two significant financial incentives for investing in a PV system and creating solar energy on your own home. The Federal Government is responsible for the Solar Credit Scheme, which reduces the full cost of the system and provides a generous point of sale discount. This scheme has been designed to taper off over time, so the sooner you purchase your system, the better.

Following success in countries such as Germany and Spain, various State and Territory governments in Australia have adopted feed-in tariffs. Under these state-by-state schemes, your energy provider is obliged to buy back the energy you export to the grid at a price equal to or above market rates.

5 Is your REC (Renewable Energy Certificate) discount locked in from when you deposit?

This can affect the price of the system significantly if it is not locked in.

This depends on which Installer you select.  A number of installers state in their Terms & Conditions that they will incorporate the costs of the REC whether or not this has increased from the time of deposit to installation. However, if this is not stated explicitly,  then it is something to consider as it can potentially affect the final cost of the system upon installation.

6 Why is this particular system being recommended to you?

Your Solar Choice Broker can discuss with you what system sizes and configurations are possible for your property, and what is available in your area in terms of Installers, panels and inverters, and financial incentives. You can discuss with them your energy usage and how much electricity differently sized systems can produce. Then, based on your budget and priorities they can provide you with a range of options. Ultimately, the choice is up to you.

7 Will the company quoting on the system also be doing the installation?

The answer to this depends on the individual company.  Some installation companies have teams of their own installers who are trained by them and work exclusively for them. Alternatively, installers may use sub-contractors who work for several different installation companies. Just because an installation company uses sub-contractors, this does not mean the quality of work is diminished.  One measure to check is that both the installation company and the electrician/sub-contractor are accredited and certified by the Clean Energy Council.  Generally, utilising sub-contractors allows a company to broaden its geographical reach and installation capacity.

8 Does the company have a proven track record in solar installations? Are they an accredited installer with the Clean Energy Council?

Just like in any market, different companies have different track records. Some have certainly been around for much longer than others. Your Solar Choice Broker will be happy to discuss what options are available to you if this is a priority. Solar Choice works with a network of installers, all of which are accredited with the Clean Energy Council, and is continually updating our knowledge base with market relevant information. It is important to keep in mind that Solar Choice provides impartial information, and is able to assist you with your research and due diligence.

9 Does the Installer use the correct DC cable rather than the AC cable?

The wrong cable can reduce power yield and reducing productivity by thousands of dollars over the lifetime of the system. This is a critical part of your system to ensure the power is used most efficiently.

This is something that the installation accreditation course covers in detail, so you can be very confident that your Installer will be using the right cable for the right position “ but it is worth keeping in mind. If you can ask a question like this of the installer, you should receive a good answer and respect.

10 Are manufacturer warranties supported locally and how are warranty claims handled?  What happens if something goes wrong with the panels?

As with any large consumer purchase, it is good practice to check who holds the warranties on the panels and inverters. For example, if the panels are held by the manufacturer (a company based in the Zhenxiang Province of China), it may be up to the customer to remove the panels from the roof and have them shipped to the manufacturer for testing, at their own expense. Preferably the warranties should be held by the installer who supplied the panels. This way, if something does go wrong the installer will be on hand to deal with problem.

11 How long will it take from from deposit to installation?

This factor will vary depending on your choice of Installer. Lead times between Installers can range from as little as three weeks up to four months. Typically, the shortest lead times are with local installers, while the longer lead times are with the larger, multi-state installers. Should you have any questions relating to specific installer lead times, Solar Choice will be able to provide that information for you.

12 How will the system be maintained?

With very little maintenance, your new PV system will to last up to 25 or 30 years.

There is very little maintenance associated with a grid-connected PV system. All you need to do is keep the panels free and clear of debris and dirt accumulation, and have the electrical system and wiring inspected by an electrician periodically. There are a range of system monitoring devices available.

13 What racking (mounting) will be used and what is the warranty on the racking?

Standard racking components generally consist of the rail itself (annodised aluminum) and fasteners (stainless steel). The rail is made up of various clamps, plates and brackets. The racking warranty is included in the Installer’s warranty and located within the Installers Terms & Conditions. As this is an integral part of the system, especially for high wind areas, it is worth asking the Installer for specific details about the racking that they use.

14 Does the racking use both mid- and end- clamps to secure the modules?

The most commonly used option is to drill into frame-work.

If a strong wind could potentially relocate your roof, then you have bigger things to worry about than racking. However, mid-clamps are one indication of a better, more stable installation, so it is worth asking your Installer if they use them. If you are told that they will cost extra, then ask them to tell you how much extra, and for them to justify the cost. Some Installers will use mid-clamps as standard, while others will view it as an optional extra.

In any case, going Solar is a long-term investment. Your system will pay for itself many times over the course of its life. Shortcuts may save money, but in order to maximise the results and returns in the long-term, don’t forget that quality counts!

Written by Sam Bradley, Justine O’Neill, Ella Vial, Tom Chapman, Matt Lasauce, Lydia Robertson, Alex Chiddy, Tom Charlesworth, and Rob Burnett

Solar Choice Residential Brokers

© 2010 Solar Choice Pty Ltd

You can check out more informative FAQs a number of our previous blogs by clicking here.

We get asked a lot of questions and sometimes the answers just remain on the page of the article and it is hard for others to keep track of them, so we have decided to summarize some of the key questions we have faced here is a summary of answers to frequently asked questions.

Why does pricing differ so much from one quote to another?

There are a number of factors that contribute to this disparity, and most of them are fairly common sense. Consider your options of installers to fall somewhere on a line with two extremes: large, national installation companies and local installers.

As a general rule, large companies streamline their business models and essentially offer less service with better prices. They do this by ordering components in bulk, large community promotions, linking together installations whenever possible, hedging a value on their REC’s and streamlining customer service. Local options spend more time in customer service and care, but offer more moderate to premium prices and products to distinguish themselves.

A quick note on product: Your local installer is aware that they cannot compete with the large companies on the competitive prices, so he won’t usually bother with the cost-effective panelling or inverters. The larger the company, the more they have the capacity to go competitive, and in trying to hit that market-leading price this will often mean more cost-effective components. This doesn’t mean they don’t offer premium component systems as well, so if this is where your interests are, be sure to check what options are available from all avenues.

The appropriate option comes down to your individual needs and expectations. The trick is to compare what you’re getting (product and service) with what you’re paying. Check the reputation of the components online and review the size and history of the company from their website. Don’t expect hand-holding from the national installers or rock bottom low prices from the blokes next door. Do expect to be treated fairly and honestly and that the product and installers are fully licensed, accredited, tested and approved by the International Standards IEC61730, as well as either IEC61215 or IEC61646. All installers on the Solar Choice network abide by these standards in all respects.

What products are proven beyond doubt to be superior and worth premium prices for?

Impartial advice is to not believe claims that any one product is the best. The vast majority of testing is subjective and the reality is that no panel has been tested where you are looking to install it; on your property.

i.e. Claim: ˜Panel X is the most efficient panel on the market’
Testing Conditions:

• Conducted at Latitude -31.802893, Longitude,146.777344;
• Operating temperature 35°C;
• ABC brand inverter;
• Pitch of 25°;
• Azimuth of 65°.

The only way that a panel or inverter brand becomes highly regarded is through decades of success on a technical and practical level. The brands that hold reputations such as this can be identified by speaking with your solar broker, or carrying out some quick diligent research on the internet.

As far as products to be avoided, so long as those international standards are in place and the product passed for use in Australia then you’ve done as much as is expected from a residential customer. Find the system that suits your budget and remember the diligent research that Solar Choice has carried out on all installers active on our network.

n.b. If you’re looking at commercial or industrial applications where a more in-depth and long term analysis of product is recommended, then our commercial tender managers can be contacted by placing an enquiry on our website via the standard sign-up process.

Why does the Solar Credits amount change from installer to installer?

The Solar Credits Discount Scheme is based on the total value accrued for the Renewable Energy Certificates (REC’s) generated for the project. Whilst the number of RECs stays the same from installer to installer for a project, the total value for the amount of REC’s alters based on what price they are sold for.

The RECs have a market value, but this fluctuates based on market trends. In addition to this, a number of installers, usually large national companies, trade their RECs via hedged price agreements with buyers, so they can actually sell their RECs for better than market rates. This is because they install so many more systems and obtain many more RECs, therefore exercising greater bargaining power on the market. These agreements are usually held in discretion, so don’t be surprised by the often confusing differences or lack of information disclosed by installers about their REC value.

For example: A 1.5kW system installed in Sydney (postcode-2000) generates 155 RECs.

1. A local installer’s quote, using the current market rate of $36 per REC, offers a Solar Credits Discount of $5,580.
2. A state-wide installer quotes, using their hedged price of $38 per REC, thus offering a Solar Credits Discount of $5,890.
3. A national installer quotes, using their discrete hedged price of $40 per REC, and thus offering a Solar Credits Discount of $6,200.

Is pricing going to increase or decrease in the near/distant future?

There are two different sides to this story, one much more persuasive than the other.

The argument for decreasing prices would highlight increased efficiency of trade lines into the country, component technology developing and reducing in price, installer competitiveness growing and REC value’s climbing.

The opposing argument needs only one of two points to trump all of the above. Basically, have no doubts that government incentives will decrease. This will mean more outlay, less return and less choice.

The Office of the Renewable Energy Regulator (ORER) moderates the discount schemes and ensures that the pricing remains competitive. They have the power to alter the discount and make it less effective when they see fit to ensure that pricing never becomes too cheap. They are considering a reduction in the number of RECs generated for residential installations before the end of 2011 in line with this.

In addition, the state governments all review the generosity of their feed-in tariffs and reduce them as time goes by in order to slowly ease of the pressure on energy wholesalers and retailers. As both of these incentives decrease in their value, prices will remain at least as expensive and more importantly, systems will earn less via a reduced feed-in tariff over their lifetime.

What is the difference between Monocrystalline, Polycrystalline and Thin-Film panels?

Monocrystalline will be completely knocked out by shade in most instances, and takes up about 8 square meters per 1kW. Polycrystalline is only slightly less efficient and usually cheaper so it can be a great option for a rounded system. Thin film will only suffer marginal and isolated losses to shade, and will take up about 12sqm per 1kW (50% more). Remember that if your panel is less efficient you just need more of them, so if your roof space is large enough don’t let these differences guide your decision.

What is the point of having a larger capacity inverter?

A larger inverter allows the system to integrate additional panels at a later stage. Therefore, larger inverters are only used for upgradeability purposes.

However, inverters work best when they are interpreting a voltage that is around their nominal output. The nominal output of an inverter is the figure that is detailed to you in quotes and in Solar Choice quote comparisons. Quite simply, it is the kW measurement of when the inverter is working at its perfect rate. If the output of the system (the total kW when adding all of the panels together) is far from the nominal output, the inverter will not work as efficiently.

From this, two deductions can be drawn. One, do not install a system where your output is much less than 75% of your inverters nominal output. Two, due to efficiency losses from a myriad of factors (y) such as dust build-up, cloud, not perfect orientation/tilt of the panels, your (x)kW system is actually going to be producing on average (x “ y)kWh a day. So the best system for your inverter actually has slightly more of a capacity to the panels than the nominal output of the inverter. i.e. a 2.2kW system with 2kW inverter. 10% is a wise maximum to consider along these lines.

How much roof space will my solar energy system occupy?

For flush mounted systems:

• Monocrystalline = 8 square meters per 1KW (10kW = 80sqm)
• Multicrystalline (Polycrystalline) = 8.5 square meters per 1kW (10kW = 85sqm)
• Thin-Film Amorphous = 12 square meters per 1kW (10kW = 120sqm)

For ground mounted or tilt framed system the difference is considerable, so better to enquire with us directly upon the specifics. Email sales@solarchoice.net.au or call 1800 78 72 73.

How do the REC’s work, and is anything required from me to receive the Solar Credits Discount?

Every year the biggest 100 polluters in Australia must account for their immense emissions by handing over a certain number of REC’s to the government. This number is proportional to the amount of pollution they produce. The REC’s are generated every time someone installs a renewable energy source in the country. The REC market provides an avenue through which the holders of these RECs can eventually sell them to the polluters to compensate themself for the price of installing the renewable energy source.

All of the complexity regarding REC market value, installer trading and hedged pricing agreements can be condensed into this one explanation: sell your RECs to your installer for a reasonable price and consider it as the polluters chipping in to pay for your solar/wind/hydro systems installation. Do this by following your installers’ instructions and filling out the forms they provide you. That is all you need to do to claim the Solar Credits Discount.

Why is a tiled roof or a double storey installation more expensive?

Colourbond and steel rooves are simple for solar energy installations. The installers can simply screw the racking straight into the material without compromising water or structural integrity. However, tiles are brittle and would break under similar treatment. Installers therefore must screw racking into the material underneath the tiles and replace them carefully to preserve the roof’s reliability. This should cost you between $100 to $200 and is a completely understandable and justifiable expense.

Double storey rooves require extra safety equipment and precautions to be used by installers. This is for OH&S reasons primarily, so having easy access does not affect this at all. It should usually cost $200-$400 for this charge, and again, it is completely justifiable.

How many kWh’s will my system produce per day?

Across the latitudinal lines in Australia and on average:

• Brisbane and above: 5kWh per 1kW system per day
• Between Brisbane and Adelaide, including Perth and Sydney: 4.5kWh per 1kW per day
• Melbourne and Hobart: 4kWh per 1kW per day

This is the most helpful and accurate guide to the number of kWh per 1kW system installed we have found. It assumes the system is between 80%-100% efficiently positioned:

http://www.solar4power.com/solar-power-global-maps.html

What do the different warranties (performance, manufacturing and installation) encompass?

Performance warranty is 25 years minimum for approved systems and only applies to the panels. It refers specifically to the gradual degradation of the solar cells in the panel. This usually accounts for a 10% drop in output due to this degradation in the first 10 years, and a further 15% in the latter 15 years. Some panels perform up and above this standard.

Warranty on manufacturing applies to both the panels and the inverter and involves any aspect of the manufacturing that if performed incorrectly could affect performance. Imagine for instance that one of the connector ports for the leads between the panels was not screwed in properly by the robot/manufacturer, and this resulted in a loss of output from the system. This would be a typical manufacturer’s warranty issue. Minimum for panels and inverters is usually 5 years.

Installers warranty applies to any aspect of the installation that if incorrectly performed would result in performance losses. If an installer dropped a panel off the ladder when installing the system for instance and this damaged the framing affecting performance, this would be an installer’s warranty issue.

As you might imagine, the vast majority of issues regarding both manufacturing and installer’s warranties would become obvious within the first year of the systems performance. It is for these reasons we don’t recommend customers becoming too concerned about the small differences in these warranties when deciding on their appropriate solar quote. Consider the warranties, but again don’t let them drive your decision.

What has to happen with the relevant electricity meter upgrades, and who is responsible for this?

This depends primarily on your solar installer and their integration of this process into their business models. Most installers will assist you with the forms and guide you through the process, but once your system is approved by your wholesaler you will be responsible for booking in the meter install with a level 2 qualified electrician. This is not an overly painful process and will cost you from $250 to $500, depending on the complexity of your meter box. On the other hand, some installers will take care of this whole process for an extra fee of the same amount. Finally, we have installers that include the price in their quote, and whilst they are rare, the extra service can be a load of your mind.

Do any of the installers offer finance?

Yes, simply ask your solar broker about which ones and what sort of arrangements they provide.

Are the economic benefits of the system taxable?

For all residential installation the system is not taxable. The only aspect of the systems operation that must be claimed is if you are sent money from your provider for surplus and are claiming a pension or Centrelink allowance of any kind.

For all commercial and industrial installations that involve installing a system on a business, every aspect of the system is taxable:

• The GST can be claimed back for the system, further reducing the cost;
• The income earned from the system must be claimed
• The system can be depreciated over 10-20 years depending on the outstanding ATO ruling.

How much money will my system make me? What calculations are used to work this out?

It all comes down to the feed-in tariff that the system is connected under. This rate differs from one state to another and also via the electricity providers. The big difference is between the Gross states and the Net states and the rate being paid.

Gross States: Simply multiply the amount of energy that is expected to be generated by the system per day by the rate your provider is paying and you will have your average daily income.

Example of a 2kW system installed on home in NSW

Assumptions: AGL is the electricity provider, currently paying 8c over the 60c gross rate minimum. Usage of the property does not affect return as this is a gross state.

2kW x 4.5kWh per 1kw per day = 9kWh generated from solar each day
9kWh x 68c (rate paid under gross tariff by AGL) = $6.12 per day

Net States: This is more complicated. You must establish how much energy is going to be generated by the system, minus off the daylight hour energy usage, then multiply the surplus by the tariff rate. The units from the solar system used up by the property still save those units from being purchased from the grid, so they add marginally to your economics

Example of a 3kw system installed on home in SA

Assumptions: The house consumes 5kWh over the sunlight hours each day. Origin is the electricity provider, currently paying 6c over the 44c net rate minimum.

3kW x 4.5kWh per 1kW per day = 13.5kWh generated from solar each day
13.5kWh “ 5kWh = 8.5kWh in surplus, and 5kWh saved from being purchased from the grid
8.5kWh x 50c (rate paid under net tariff by Origins) = $4.25 per day and
5kWh x 18c (Market rate for electricity purchased from grid) = $0.90

Total earnings from system per day: $5.15

Are the Australian, German or Japanese panels justifiably more expensive than Chinese panels?

At the end of the day, there are differences between panels. The international standards keep everything in the same ballpark, but panels and inverters will still outperform others in time. Take the stress off yourself and contact a Solar Choice broker if this is one of your more pressing matters. Think about your priorities, identify them, email us (sales@solarchoice.net.au) and let us make a suggestion that is appropriate for your project. It’s that easy.

How much efficiency do I lose without tilt frames?

You will lose between 15-30% of total output each day. This amount is significant, which is why tilt frames or alternative flat-roof designed systems are recommended. Remember that most city councils are far stricter on the need for Development Applications when panels are not flush mounted to roofs. If you have a flat roof, contact us and we will run an analysis on whether tilt frames or flat-roof designed options suit your project more appropriately.

Are panels hail proof?

All panels that hold the international standards (which they all do in Australia) have been tested to hail and impact damage. A one in a thousand year event will still damage them, but the standard hail storm has been tested against and the panels hold up fine.

Does the inverter need to be near the meter?

It is recommended, however, the inverter will be positioned on site in the most appropriate place. This may be a garage, laundry or meter room. The distance between inverter and meter should not exceed 20 meters to avoid transmission losses.

What happens if one of my panels is in shade?

It will stop working. It may knock out all other panels in the ˜string’ as well. Depending on the size of your system, this can mean huge losses in output. Always avoid shading completely, and if you cannot, contact your Solar Choice Broker for advice. Thin-film panels are more shade tolerant, but the system will face losses regardless. If you have only got a heavily shaded area, just like if you’ve only got a South facing roof area, then solar energy is not recommended for you.

Will it work if I have panels on more than one side of the roof, and how?

Usually it is only recommended to split the system up over multiple roof areas if you have an inverter that can read the arrays separately, all aspects and tilts are identical, and none of the areas are subject to shade. Inverters that have Dual Tracking (Dual MPPT inputs) allow panels to be split over two completely different areas; however these are usually more expensive. Please note that MPPT Tracking is not Dual Tracking, and most inverters had one MPPT Tracking listed on their technical specifications. Only a Dual-input MPPT inverter can split the system independently.

Written by Jarrah Harburn

Senior Solar Energy Broker

Solar Choice

© 2010 Solar Choice Pty Ltd

Last week in “The Manufacturing and Science behind Solar Energy Panels” we talked about the different types of solar panels you could purchase and what all those complicated names meant. This week we shall focus on all the reasons why your cells might not be performing up to specification and whether its a temporary problem or it’s something you need to contact your installer about.

Before we begin to focus on the area’s where a loss in efficiency can take place it is important to get the basic assumptions of how a solar cell works out of the way. In short in the diagram above a “Cross-Section-of-a-Solar-Cell” light will enter from the top and after passing the anti-reflection coating enter the emitter layer and depending on the wavelength of light that enters the cell, this wave of light will excite the electrons in the emitter and/or base after which they get collected by the busbars and transmitted to load.

There are several areas where a loss in efficiency can occur however the biggest area or cause is always optical, and that makes sense because a cell can only generate energy from the light it is able to absorb.

1) Front surface soiling – this is when the surface has been covered with dirt or pigeon droppings and doesn’t get washed by the rain. This causes areas of the cell to not be able to absorb light as effectively.

Making physical inspections and spraying water on your modules can help reduce the problem.

2) Finger design – this is the concept of balancing the pros and cons of big vs busbars so there is a greater ability to collect the electrons that get excited by the light that enters the cell and lower area that directly blocks light from entering the cell.

This dilemma is optimized through rear-surface-contact cells and buried contact cells.

3) Partial shading – this is when part of your solar energy panels are being shaded by a cloud or another object and this causes a larger problem which is called mismatch across the several cells that are joined together in series. What this means is that when 3 out of your 36 cells in your panel are shaded the drop in performance is limited by the 3 cells. Thankfully there is a solution to this and they are called bi-pass diodes, this allows the performance to not be limited by the 3 cells by cutting them out of the system when their performance drops.

This is something you can ask about when you purchase you panels as this helps reduce the drop in performance during the uncontrollable weather issues.

There are several other areas of loss but thankfully the panels you purchase and the warranty that you get from the respective company takes this into account before they rate a panel at a certain power output.

If you would like to know more about these losses let us know.

Written by Prateek Chourdia

MEngSc – Photovoltaics and Solar Energy, UNSW

Solar Energy Analyst

Solar Choice

© 2010 Solar Choice Pty Ltd

Sources:

“Applied Photovoltaics” by Stuart R. Wenham et. al.

“Solar Cells” by Martin A. Green

To Feed-in or not to Feed-in: Encouraging renewable energy electricity production

The concept of a feed-in-tariff (FiT) has been around since the 70′s but it was only in the last decade we saw Germany pioneer its usage to dramatically increase electricity generation from solar PV.

Now over 30 countries, including Australia have adopted feed-in-tariffs to encourage the production of electricity from renewable energy sources. Those of you with PV solar systems most likely purchased your system due to the existence of a feed-in-tariff in your state and are just kicking back to wait for their returns. Unfortunately economists, the electricity wholesalers, and large-scale renewable developers are not always in favor of these generous premiums that are driving the solar PV market and drastically reducing your energy bill.

Some Background on Australia’s incentives

Small-scale renewable energy projects in Australia are currently supported financially through RECs (Renewable Energy Certificates) and FiTs (Feed-in-Tariffs). Most countries either have one or the other, which is why some economists believe the federal Renewable Energy Target and its REC trading scheme should operate by itself, without the assistance of various state-based FITs, favouring the most efficient renewable energy technology at least cost. And so the question on policy makers’ lips is whether we are spending too much money on integrating renewable energy into Australia’s energy mix with our feed-in-tariffs.

The clear answer and reality of the situation is that a feed-in-tariff is the quickest method to reaching a certain capacity of renewable energy generation:

1. It provides security to clad your everyday electricity warrior (the single mum, the struggling farmer, you and I)  with ammunition against rising energy bills which are becoming more expensive because of network upgrades, completely unrelated to the generous Feed-in-Tariffs!

2.  It ensures that the REC Market doesn’t pick winners of large scale Wind or Hydro projects and encourages investments into smaller-scale technologies, which stimulates demand and R&D, making them more affordable.

3. It creates more jobs than a big development and reaches a target of renewable energy capacity far quicker than any other mechanism – the quicker we install renewables, the less dependent we become on dirty coal for our base load requirements.

How You make your money

There is no doubt about it, that both renewable energy policies: RECs and FiTs, have improved the economic viability and payback time for your average household PV installation. RECs bring down the upfront cost of the solar installation for small businesses and residences and the FiT, normally capped at 10kw for most states, earns you a fixed return based on the nature and duration of the scheme (i.e. 7 years Gross, or 20 years Net). NSW homeowners for instance, can purchase a 1.5kw system for as low as $2-3000 (after RECs) and earn over $1400 per annum for the next seven years.

The most attractive scenario would be a national gross feed-in-tariff (similar to Germany’s and now the UK’s) as the quickest way to reach a certain capacity of electricity generation from renewable energy in Australia.

The Concerns vs Benefits of Feed-in-Tariffs for Small renewable technologies

Large-scale developers are not overly excited with the surge of the domestic market and lament the lack of incentives that are available to them which has now been resolved with the fixed REC price for small renewables at $40. From previous customer experiences it does seem as if electricity wholesalers, the bodies that maintain the electricity network, will begrudgingly have to update the network to incorporate solar PV customers wanting to export onto the grid. If there is a large supply in a particular community then there may be too much for the grid to handle in some areas and this is a possible solution in the future. However until then there are a large number of benefits that outweigh the current gripes out there about Feed-in-Tariffs.

Below is a table that displays how such concerns are outweighed by the multiple, realistic benefits that FITs and small-scale renewable policies have to offer:

I hope this was useful information to those of you wondering whether Feed-in-tariffs will be important to us in the future. And as per our previous Solar Choice Blog please have a look at which electricity retailers are offering the best feed-in-tariff rates, above and beyond what is stipulated by their respective governments.

Renewable Energy Consultant/Senior Solar Energy Broker

Brendan Noakes

Solar Choice

© 2010 Solar Choice Pty Ltd

Yet another reason to go solar!

In the second half of this year mandatory disclosure will be introduced for commercial office buildings with a leasable space over 2000 square metres. Environmental Performance Disclosure will then be phased in for all residential premises across all Australian states and territories by May 2011. So………

1.     What is ˜Environmental Performance Disclosure?

2.     How will it affect me and my house?

3.     How can you make the most out of Environmental Performance Disclosure?

1. What is ˜Environmental Performance Disclosure

I    Environmental Performance Disclosure will be the requirement for houses, flats and apartments to provide open information on the energy, water and thermal (efficiency and running costs) of the dwelling.

II     To do this homes will be assessed and a rating (most likely in stars) will be created for every home.

III     This rating will be required for and then be openly labeled in any communications on the selling or leasing of a property.

2. How will it affect you and your home

I     Increasing the water and energy efficiency of your home will increase the (star) rating of your home.

II     Increases the star rating of your home will make it a more desirable purchase and hence increase the value of selling or leasing your property.

3. How can you make the most out of Environmental Performance Disclosure

I     By maximising the environmental (energy and water) performance of your home you can also maximise the value of your home.

II     To maximise the homes performance the easiest retrofits available for your home include installing Solar Energy Panels (Photovoltaics), Solar How Water, Rainwater Tanks, and insulating your home.

So now Solar Energy (from Photovoltaics) will not only be a great benefit, due to generous rebates and Feed in Tariffs and extremely competitive prices, it will also be a very recognisable capital investment in your home which can be easily measured by creating a marked and measurable increase in the environmental(star) rating of your home.

A link to the government website with more details on EPD can be found below:

www.environment.gov.au/sustainability/energyefficiency/buildings/homes/index.html#new

Iain McGregor

Commercial Tenders Manager

Solar Choice

© 2010 Solar Choice Pty Ltd

(There have been a number of changes to feed-in tariff policy across the Australian states–most notably that the NSW Solar Bonus scheme has been suspended. Please see our feed-in tariff page to see what solar incentives are on offer in your state!)

You may be wondering, if I install a 1.5kW solar PV system, how much energy will I be feeding back to the grid? This is an important question, especially if your state has a net feed-in tariff. The answer depends on two things – how much energy you produce, and how much you consume.

(Get a free comparison of solar quotes from the installers who operate in your area, anywhere in Australia!)

A previous article on this site looked at the first part of that answer, how much energy your solar cells will produce. Here we learnt that the amount of energy a 1kW system produces varies depending on where it is located in Australia.

The last two articles in this series have explored the second part of that answer; how much energy you consume in your home (How do I use electricity throughout the day “ the load curve and How to save energy in your home). They told us what we use our energy on, when we use it, what uses most of it and also some hints on how to use less. Here we also learnt that the amount of energy the typical home consumes varies depending on where it is located in Australia.

In this article, we stitch those two parts together to find the answer to the question of how much a typical home in Sydney will export to the grid.

Consumption versus generation in Summer

The graph below shows three curves for an average Summer day in Sydney:

1) How much electricity the typical household would consume (the red line)
2) How much electricity a 1.5kW grid connected solar PV system will generate (the solid green line)
3) How much electricity a 3kW grid connected solar PV system will generate (the dashed green line)

How to interpret this graph

The graph below shows the amount of power being used by an average home, and generated by an average  solar PV system at any point in time during an average summer’s day. If the green generation line is higher at any point then the red consumption line, you are generating a surplus of power, and hence feeding that electricity back into the grid. When the green generation line is below the red consumption line you’re still generating, but not enough to meet your households demand, so you will be buying electricity as per normal to make up the difference.

In the discussion below you may get confused by the nomenclature of kW and kWh. They are not the same thing, one is power and one is energy. For an explanation of this please refer to the article; Physics 101 – What’s the difference between power and energy?

Average NSW household in Summer – electricity consumption versus generation

The average production of a solar PV system in Sydney has been calculated using the online performance calculator for a grid connected system; PVwatts. The attentive eye will notice that a 1.5kW system is only producing just a touch over 1kW of power at it’s peak. This is not an error. The average PV system will export only around 75% of it’s rated power to the grid at it’s peak generation due to the variety of losses associated with cleaning, inverting and transforming power from the solar cells to a usable form.

The home electricity consumption curve has been calculated from grid wide electricity consumption data for NSW from the Australian Electricity Market Operator (AEMO).

A 1.5kW system

In the above graph we can see that a 1.5kW system will produce just enough power to very slightly surpass the average household’s demand at 1pm, when the sun is at it’s peak. The rest of the time, the average household uses more than the solar PV cells can produce. In total, the 1.5kW system produces 7.3kWh of energy, compared to total consumption throughout the day of 20.5kWh for the house (for the technically minded, the amount of energy produced is the area under the curve, because energy is the integral of power).

Hence, in this situation virtually no power is exported or fed into the grid by your PV system (except for a negligible amount at 1pm) as it is all consumed by your home. This will save the money that you would otherwise have paid for electricity.

In a state (such as Victoria) with a net with a net feed-in tariff in place (where you are paid only for the SURPLUS electricity you export to the grid) you would have no feed-in tariff income. You would still, however, be saving the $1.14 in electricity you would otherwise have had to pay for. Although both the average consumption and generation curves for Victoria will be slightly different then depicted in this graph, this is more or less a representative example.

(NSW formerly offered a gross feed-in tariff. With a 1.5kW system you would get 7.3kWh x 60c/kWh = $4.38 in feed-in tariff income if you signed up before 27 Oct 2010. Unfortunately, no tariff is on offer for those who sign up since the scheme ended, and no guarantees will be made until April 2012. However, there are still compelling reasons to get a solar system in NSW!)

A 3kW system

The dashed green line shows the electricity generation of a 3kW grid connected solar system. As you can see, this is above the red line for the majority of daylight hours, meaning you will be exporting a good amount of energy to the grid.

In total, the 3kW system produces 14.5kWh of energy, compared to total consumption throughout the day of 20.5kWh for the house. But because it is often producing more at any given time then the household can consume the 3kW system exports a total of 6.02kWh of energy to the grid.

The rate you are paid for your surplus electricity fed into the grid will depend on which state you live in. (Read about state-by-state feed-in tariffs.)

As a representative example, if this system was in Victoria where a a net feed-in tariff is in place, you would earn:

6.02kWh x 60c/kWh = $3.61 in feed-in tariff income (6.02kWh is the net (surplus) amount of solar energy generated and exported to the grid)

as well as save:

8.5kWh x 15.6c/kWh = $1.32 in electricity you would otherwise have to pay for.

Giving a total benefit of $4.93.

(Under NSW’s now defunct gross feed-in tariff scheme, with a 3kW solar system you would have brought you a total benefit of 14.5kWh x 60c/kWh = $8.70 in feed-in tariff income. 14.5kWh is the gross amount of solar energy generated.)

Consumption versus generation in Winter

In winter, the expected solar PV average generation curve is slightly lower then in summer, reflecting the lower intensity of the sun. Note that on a cloudy day generation will be much lower then depicted. In Sydney, where the sun shines almost perenially, this is not such a problem. Melbournians, however, are less lucky! In this graph average household electricity consumption is represented by a blue line. For a discussion as to why it takes this shape, please refer to the article How do I use electricity throughout the day “ the load curve.

Average NSW household in Winter – electricity consumption versus generation

A 1.5kW system

In the above graph we can see that a 1.5kW system will never fully meet an average household’s demand. In total, the 1.5kW system produces 5.3kWh of energy, compared to total consumption throughout the day of 26.7kWh for the house.

Hence, in this situation no power is exported or fed into the grid by your PV system as it is all consumed by your home. In NSW, where a gross feed-in tariff is in place (where you are paid for ALL the solar energy you generate) you would earn:

5.3kWh x 60c/kWh = $3.18 in feed-in tariff income

as well as save:

5.3kWh x 15.6c/kWh = $0.83 in electricity you would otherwise have to pay for

Hence, in NSW a 1.5KW system for an average household on a Winter day has a total benefit to you of $4.01.

In a state like Victoria, however, where a net feed-in tariff is in place (where you are paid only for the SURPLUS electricity you export to the grid) you would have no feed-in tariff income. You would still, however, be saving the $0.83 in electricity you would otherwise have had to pay for. Although both the average consumption and generation curves for Victoria will be quiet different in winter due to the prevalence of gas heating, this is an illustrative example.

A 3kW system

The dashed green line shows the electricity generation of a 3kW grid connected solar system. As you can see, this is above the blue line for the majority of daylight hours, meaning you will be exporting a good amount of energy to the grid.

In total, the 3kW system produces 10.5kWh of energy, compared to total consumption throughout the day of 26.7kWh for the house. But because it is often producing more at any given time then the household can consume the 3kW system exports a total of 4.02kWh of energy to the grid.

In NSW, where a gross feed-in tariff is in place you would earn:

10.5kWh x 60c/kWh = $6.30 in feed-in tariff income (10.5kWh is the gross amount of solar energy generated)

as well as save:

6.5kWh x 15.6c/kWh = $1.01 in electricity you would otherwise have to pay for (6.5kWh is the amount of generated solar energy your house is consuming)

Hence, in NSW a 3KW system for an average household on a Winter day has a total benfit to you of $7.31.

As a representative example, if this system was in Victoria where a net feed-in tariff is in place, you would earn:

4.02kWh x 60c/kWh = $2.41 in feed-in tariff income (4.02kWh is the net (surpluss) amount of solar energy generated and exported to the grid)

as well as save:

6.5kWh x 15.6c/kWh = $1.01 in electricity you would otherwise have to pay for

Giving a total benefit of $3.42.

How to boost your solar generation above consumption

There are two ways you can boost your generation above consumption, and hence export more energy to the grid.

One way is to first lower your consumption of energy. The previous article, how to save energy in your home, provides some practical hints on how to do this. In particular, for the purposes of the net feed-in tariff it is advantageous to focus your efforts on saving energy during daylight hours when your PV cells will be generating electricity. Another strategy would be to shift when you use appliances, for instance, run the dishwasher at night instead of during the day. Although maximising your solar feed-in tariff, this does not have any positive environmental outcome. Hence, the best action you can take as a environmentally conscious citizen is to try and reduce your energy consumption overall and become more energy efficient. This way you’ll earn more from a net feed-in tariff, pay less in energy bills and use less brown electricity.

The other way to maximise the difference between generation and consumption is to simply install more solar PV generation capacity. This has been demonstrated in the above examples by the observation of the differences between a 1.5kW and 3kW solar PV system. Different states have different capacity limits for installed PV generation (read about the status of feed-in tariff schemes in each state) so make sure you’re within these. If you can’t install a bigger system because you’re near the capacity limit or have run out of available roof space, another way to further maximise your generation is to install a solar tracker.

Kobad Bhavnagri
Solar Energy Consultant
Solar Choice Pty Ltd

© 2010 Solar Choice Pty Ltd

The previous article, how to save energy in your home, told you how on aggregate you use electricity in the home – that is, what percentage of your power is used by certain appliances. But how do you use electricity during the day, hour by hour? What appliances are on and when, and how does your consumption look in the morning, evening, afternoon and in the middle of the night? This information is of great interest to households with solar PV cells, as they would like to know how to maximise the amount of energy they export to the grid, particularly when their state has a net Feed-in Tariff.

This answer to this question is in what electrical engineers and energy analysts call the “load curve” or “load profile”. It’s a graph that shows us what electricity consumption is at different times of the day, and what the components that make up that total are at different times. The load curve for a typical home is actually different in each state of Australia due to climatic variations, the usage of gas for heating and hot water, and different home appliance penetration rates.

The summer load curve

There are two very distinct load curves – one for summer and one for winter. In actual fact the load curve for an extremely hot summer day is quite different from a mild summer day (basically because of air conditioning) as it is for a very cold and mild winters day (due to heating). As an interesting little fact, engineers can tell when a really important football match is on in England because everyone turns on their kettle at half time, and you can see this on the national load curve! Nevertheless, we can generalise to get a typical load curve for summer and winters days.

The graph below show us how we use power on a summers day in NSW. It is only the load curve for households across NSW (commercial and industrial load curves, once again, look quite different). It is broken down into a rainbow of slices that depict what appliances are using power and when.

The graph starts at midnight, and surprisingly, at this point in time it is at its zenith. Why is this? Won’t most people be in bed, or winding down for sleep then? The answer is hot water. As the cream coloured section of the graph shows, all the off peak electric hot water heaters are programmed to come on in full force at midnight and 1am (to take advantage of cheaper electricity at night), and this consumes a massive amount of power.   

As you would expect, the load curve goes down a lot in the wee hours of the morning when everyone is asleep and using little energy. However, it doesn’t go anywhere near zero, because a whole lot of appliances like fridges, freezers, hot water heaters and standby equipment are still on. Notice that they make up a very uniform stripe of consumption – they are always on, and hence take lots of energy over the course of the day. 

The load curve then builds in the morning and has two little spikes, one for morning tea and one for lunch. You’ll notice that those two little bumps are mainly caused by people using hot water on demand, and hot water tanks needing to replenish used up water. A lot of dishwashers, kettles and cooking appliances tend to come on at this time too.

After about 1pm the airconditioners start to come on and the load profile really starts to climb. By 5pm they are on at full steam. At about this time people come home from work and school and turn on all of their lifestyle appliances such as TV’s, cooking equipment as well as lights throughout the home, adding to the peak.

This starts to settle down at around 9pm as people begin winding down, but then 9:30pm the hot water off peak ramp up begins, and demand soars back up.

As you can see, air conditioners, hot water heaters and refrigerators are the dominant parts of this diagram. And this is reflected in the previous article how to save energy in your home, where they weighed in at 23%, 37% and 12% respectively.

The summer electricity load curve for households in NSW
Source: EMET Consultants Pty Ltd

The Winter load curve

The winter load curve is markedly different from the summer one, basically because of the effect of temperature. It is characterised by the twin peaks or morning and evening, whilst summer is a big hump in the afternoon. Winter starts off at midnight in much the same way as summer, with off-peak hot water heaters on at full steam. However, you’ll notice in comparison that it’s much higher in total, almost by 1000 mega watts for the whole state. This is because in winter, hot water takes even more energy to heat up then it does in summer (the water starts of colder).

As the hot water heaters ramp down the wee hours of the morning look much the same as they do in summer. Notice, however, that the stripe of consumption for refrigerators is comparatively lower, as they now have to work less hard as the air outside is cold.

Now the differences really begin. People begin waking up and straight away turn on heaters, lights and take hot showers. This causes the morning spike, which gradually eases off throughout the day as people stop using hot water and turn down heaters. In winter the middle of the day is quite quiet, but in summer, as we saw before, things are on the move.

At 5pm the explosion in demand starts again, and the hot water, heating and lighting load is coupled with cooking and entertainment, making it peak at about 7pm as people watch the news and cook dinner. Eventually this eases down before the same 9:30pm spike that happens as in summer for hot water heating.  

 The winter electricity load curve for households in NSW
Source: EMET Consultants Pty Ltd

These graphs show how electricity consumption is primarily driven by temperature. A lot of the little things we do, that we don’t quite realise, are what govern our energy consumption.

So how does my consumption of electricity compare to my generation via solar PV cells, and how can I maximise the difference to attain the best net Feed-in Tariff? This topic will be addressed in the next blog.

Kobad Bhavnagri
Solar Energy Consultant
Solar Choice Pty Ltd 

© 2010 Solar Choice Pty Ltd