The Solar Choice blog is full of good advice. We have written about how to orient your solar panels, how to determine what size system you’ll need, how much you might expect to earn or save through government solar power incentives (feed-in tariffs and RECs) with a solar PV system, and how to troubleshoot electricity production issues with your system, plus a number of FAQs about related topics. Recently we came across a satellite photograph demonstrating something you might want to keep in mind when you install an array on your roof: Trees have a tendency to grow over time!

When these panels were originally mounted, the trees now causing problems may have been mere saplings. A clear reminder to keep an eye on your trees so that they don’t sneak up on your solar power array.

Solar photovoltaic arrays don't do much good if the sun never manages to reach them...

Written by James Martin, image stumbled upon by Alex Chiddy

© 2010 Solar Choice Pty Ltd

Determining the orientation and tilt angle of your solar power generation system is one of the most important considerations in designing your solar power system. As we have mentioned before, in the southern hemisphere, due North is the optimum orientation for panels. But not everyone has a perfectly oriented roof. When your two best options are East or West, which should you choose?

During the course of a day, the sun passes through the sky in a particular arc that varies throughout the year due to the earth’s orbit (see top image). The arc is always symmetrical from East to West, measuring out from the centre point, which would be midday. This means that from sunrise to midday (not counting during daylight savings time) and from midday to sunset, there is an equal number of hours of sunlight on one particular location. (You can see how this applies to your particular location using applications like SunCalc, which shows you exactly how the sun moves through the sky at different times of day.)

So, if your home or roof does not have a Northern aspect, but does have two roofs that face due East or due West, you may be asking yourself which side would be a better location for the most power generation. Making the right decision will impact on how much money you can save or possibly even make under the solar power incentive schemes available throughout Australia.

The first thing to consider is shading, of course, which can potentially have a big impact on the productivity of your system. Is either side of the roof shaded by nearby objects? If one side is shaded, choose the other side.

If you’ve determined that the shading effects are either non-existent or basically the same on both sides, then the next thing to consider is the angle of your roof–if possible, you don’t want to have to put in any mounting brackets or solar trackers. The two sides of your roof may be tilted at different angles: you will want to choose the side which is closer to being horizontal, as this will result in the most insolation (incident sunlight) throughout the day.

So, you have determined that shading is not an issue, and that both sides of your roof are symmetrically angled. What do you do now? Although Australia is well-known for its unpredictable climate, you will need to consider when you tend to have cloudy weather more often–in the morning or in the evening. This will depend on your location and climate, but for many locations (including Sydney), mornings have a greater tendency for overcast skies. Shading, even from clouds, can reduce the output of a system by up to 90%: any time it is not sunny, energy production will drop. So, in essence, the answer is that you should try to put your panels on the ‘sunnier’ side of the roof in terms of weather: if you have cloudy mornings more often, the West roof, and if you have cloudy afternoons more often, the East roof.

That being said, if you are thinking strategically about power consumption and pricing, you will want to keep in mind that in most states the price of electricity is higher around 5pm. For example, in NSW the peak electricity price at 5pm is $0.36, which is roughly twice the shoulder rate just prior to that time. If your panels are west-facing, you will be producing optimally right about this peak electricity time, potentially providing you significant savings on your bills.

Written by James Martin

© 2010 Solar Choice Pty Ltd

Sources and Links:

Previous related Solar Choice Blog Entries: Orientation and tilt angle for your solar power system : Solar Power Incentive Schemes in Australia : How to install solar panels on your roof : Solar Trackers

Thin-film solar cells installed on the Japan Pavillion at the 2010 Shanghai World Expo

In a previous Solar Choice blog entry, Prateek Chourdia wrote about some emerging trends in the future of photovoltaic solar technology, including thin-film solar power. This entry will summarise some of the salient points regarding thin-film technologies, otherwise known as flexible photovoltaics, and discuss their possible future direction.

What is a thin-film solar photovoltaic cell?

Unlike the solar panels that you probably imagine when you think of solar power (monocrystalline and polycrystalline), thin-film technology is not composed of highly refined silicon crystals, but is instead one continuous material. There are four basic types of thin-film solar photovoltaics (TFPV), classified by the photovoltaic material that is used. The principle of TFPV, however, is the same as that of crystalline PV: light strikes the material and excites electrons, which then ‘flow’ through some permutation of a p-n junction, generating electricity which is captured and utilised.

Amorphous silicon (aSi) solar PV cells:

Amorphous silicon solar power, discussed briefly in our previous blog entry, was developed in the ’70s and is a made from a non-crystalline form of silicon, which results in lower efficiency per square meter–up to 15% in laboratory conditions, but generally 6-8% in real-life applications. (Compare this to 15-18% in crystalline silicon cells.) However, thanks to its flexible nature and their relatively lower susceptibility to the effects of overheating and shading, aSi has a number of everyday applications: it has already been used for decades in charging solar-powered calculators and watches, and more recently has been developed by a number of companies into solar PV roofing materials such as tiles and shingles.

Cadmium Telluride (CdTe) solar PV cells:

A smaller number of companies have developed solar cells made of Cadmium Telluride, developed in the 1990s, which promises to rival aSi for the place of the most cost-effective means of thin-film solar power generation, with laboratory efficiencies of 16% and 11% in real life. A flexible photovoltaic cell composed of this material with 12.4% efficiency was developed in 2009 by the Swiss Federal for Materials Testing in Switzerland. Cadmium is a relatively cheap and readily available material, but Telluride is one of the rarest elements on earth. (More about First Solar’s CdTe technology.)

Copper indium gallium selenide (CIS or CIGS) solar PV cells:

Copper indium gallium selenide was developed in the ’80s and, in addition to having a high heat tolerance, it also has one of the highest efficiencies for thin-film solar material–20% in lab conditions and 11% in real-life. (More about CIGS technology.)

Organic solar PV cells

Organic solar cells are made of materials that contain carbon. The cost of manufacture of organic cells is less expensive than from inorganic materials such as silicon, but this advantage is significantly offset by the fact that the solar conversion efficiency of these cells is only 8% in the laboratory and 4% in real life, and the fact that they tend to have a short production lifespan of 6 years.

What does the future hold for thin-film solar PV?

There are a number of factors that give promise to the future of thin-film PV. It has numerous applications: it can be used as a building material in the place of awnings, in conjunction with windows, and on walls. It is also useful for smaller, portable devices to be used in areas without readily available electricity: battery chargers in the middle of the desert or in rural areas (or even while camping!). TFPV may be rolled up in some cases and tucked away into a safe sheath or container, to be brought out when needed. In fact, among other organisations, the US military is already making use of portable photovoltaics for operations in areas where grid power is absent. On top of this, with appropriate life-cycle planning, some types of TFPV can be more easily recycled than crystalline cells.

Global Business Intelligence (GBI), a market research firm, predicts that thin-film technologies will become a major force in the solar power market by the year 2020. This realisation of this prediction will be predicated on corporations’ success in ensuring higher solar conversion efficiencies and longer lifespans of these technologies.

In any event, the thin-film PV industry is a rapidly evolving one, and new technologies are being experimented with by a number of different companies all the time. If you are looking to install or use these technologies, be sure to discuss them with the manufacturer, who should know best what the capabilities of each technology are.

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Resources and Links:

MotherEarthNews.com, “The promise of thin film solar”

GBI Research: “Thin film photovoltaics market analysis to 2020″

SpecialtyFabricsReview.com: “Flexible Photovoltaics”

National Renewable Energy Laboratory, Golden Colorado, “High-efficiency CdTe and CIGS thin-film solar cells: highlights and challenges” (MS Word document)

Japan Pavillion image from TripAdvisor.com

Previous related Solar Choice blog entries: Emerging Trends in PV : Which type of solar panel should you choose? : Building-integrated PV : Roof-mounted solar system options

For most people who decide to mount solar panels on their roof, a mounting system is necessary. This short entry explains the basics of what needs to be taken into consideration when putting a solar array on your roof.

-Read about Solar Panel Tilt and Orientation in Australia-

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

Solar panels on my roof: what to consider

Ordinarily, if you have decided to install a solar power system, it will most likely be mounted on your roof unless you have perhaps become a solar farmer, in which case your system may be ground-mounted. In such a case, deciding where to locate and how to arrange your solar panels is a bit easier (provided you have the space, which is probably the case if you’ve got the option for a ground-mounted system) than working around the inherent limitations of your roof’s orientation, tilt angle, material, and available space.

Roof orientation and tilt angle for solar panels:

The orientation of your roof is the first thing to consider when considering whether you want to install a system. In the southern hemisphere, due north is the best option, but obviously, not all homes were designed with solar power in mind, and as a result, roof orientations differ drastically from home to home. Northeast and northwest-facing roofs are second best orientations after due north, followed by east and west. Anything further south than these will result in a severe reduction in efficiency to your panels. If your array faces due east or west, you will never see more than 85% performance from your panels–not that this should prevent you from going ahead with an install, but it is something that needs to be considered.

Likewise, the tilt angle of your roof will have a major impact on the amount of solar rays collected by your solar power system.  Outside the tropics, including through most of Australia, an angle of about 32° is ideal, but anywhere between 20° and 40° should be sufficient for up to 90% operational efficiency. Many roofs fit this description, but if your roof is less than 20°, you might need to consider using mounting brackets.  (Please see this previous entry about tilt and orientation for solar panels in Australia for more information.)

Roof space available for solar panels

One obvious factor to be taken into consideration when mounting panels on a roof is the amount of space available on it. A typical polycrystalline or monocrystalline panel measures about 1.6m x 1m, and depending on the capacity (size in watts) of your system, for an average 2 or 3-bedroom home, you should be able to fit enough panels to significantly offset your electricity costs on one, or in a stretch, two parts of your roof. Closeness of the panels to your home is not an absolute requirement: the roofs of sheds, garages, and balconies that stand slightly apart from your house may also provide options for placement.

What kind of roof materials are there and how are they different for mounting solar panels?

If you have a house in Australia, you probably have either a tile roof, a slate or shingle roof, or a corrugated metal roof. Tiles are hard and held together by a combination of mounting hooks and gravity–like a jigsaw puzzle. It is possible to take broken tiles out to replace them, sometimes without any special tools. Shingles and slates, on the other hand, typically have holes in them and are nailed onto the roof substrate. In both cases, they overlap each other so that water does not penetrate the building as rain falls. Corrugated metal roofs are composed of comparably large sheets that usually overlap each other, or may be one large piece. In mounting a PV system on any of these types of roofs, it is important to ensure that no gaps are left in the roof that may later result in leakage.

Asphalt roof shingles are nailed to a roof substrate, overlapping one another

Ceramic roof tiles overlap one another and are fitted together, held in mainly by gravity.

A corrugated metal roof is usually a series of sheets like the one above

Mounting a solar array on all of the above types of roof is possible and in fact quite standard practice for solar power system installers, as many installations are retrofit onto the roofs of old homes.

Types of mounting systems for roof-top solar panels

Universtal mounts:

The most common way to mount systems to first install brackets, the shape and size of which will vary with the mounting system manufacturer, but which will look something like the L-mounts pictured below. In the case of tile, slate, and shingled roofs, this may require cutting precise holes in the roof material for the mounting brackets to protrude from, while on corrugated roofs, the brackets will Rails are then fitted onto the mounts, which have been spaced appropriately apart so that the panels can be fitted flush together, side by side on the same set of rails. This is the most typical system for small- to medium-sized arrays, although flush mounts which support individual panels may also be used if the array is only composed of one or two panels. If you need to adjust the tilt angle of your array because the tilt angle of the roof is less than ideal, it is possible to do this with a universal mount by increasing the height of the rail higher up on the roof.

This Conergy solar panel mounting system consists of: brackets, rails, and panels.

Conergy mounting bracket for solar panels to be installed on Roman tile roofs

The first step in mounting a solar panel on a corrugated metal roof: L-bracket.

Conergy's hook-based system for mounting solar panels on slate or plain tile roofs. Note the metal flashing to be placed underneath the hook to minimise wear and tear.

Roof-integrated photovoltaics:

If you plan to replace your old roof anyhow, or if you are building a new home, you might want to consider photovoltaic roof tiles or shingles, which, as we discussed in our previous blog entry covering building-integrated photovoltaics (BIPV). These can be a cost effective option if you intend to replace your roof and install solar panels around the same time. Roof-integrated photovoltaics is one of the relatively more widespread forms of BIPV, and it is possible to have a solar roof installed here in Australia. (For more information, please contact us!)

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Resources and Links:

Builder Bill

Image credits: Tile Roofs : Asphalt Shingles : Corrugated Roof : Conergy Suntop III: Instructions for Professional Installation (pdf)

Previous Solar Choice blog entries: Built-in Photovoltaics : Tilt angle and Orientation for solar power systems : What kind of solar panels are right for me?

The number of small, simple ways to put solar power to use in daily life seems virtually endless, and opportunities present themselves at every corner. Solar carports are one innovative way to turn an ordinarily passive, mundane, everyday item into an electricity generation system that works for you. It’s the sort of thing that, when you see it, makes you ask yourself, “Why didn’t I think of that?”

(Get a free solar quote comparison from solar system installers in your area.)

Solar carports are a simple yet powerful form of building-integrated photovoltaics (BIPV) that cleverly takes advantage of a carport’s intended function as a sunshade by installing solar panels or amorphous solar film on top to capture and utilise the sun’s rays. The concept speaks for itself, and without much thought it is easy to look around and find opportunities throughout the world to convert driveways, car parks, car ports, gazebos, and even bus stop covers into power producers. As solar power becomes more and more affordable, implementing this sort of solution to the future’s energy demands will become a matter of course. As discussed previously in our blog, renewable energy will play a significant part in the future of transportation as well, and charging stations for electric cars at solar car parks is an idea that most people would agree makes a great deal of sense. In fact, such intelligent energy solutions are already under development or being actively employed in locations throughout the world, and although they’re not so common in Australia, they are starting to take off in Europe, the US (especially California, but also surprisingly New Jersey!), the Middle East, and Japan. Such installations would make lots of sense in different states in Australia, when taking into account the incentive schemes to install solar power systems throughout the country–the costs and benefits of solar car ports are essentially the same as roof-mounted PV!

Solar powered car park, outside Republic of Palau Parliament House. Photos by Angus Gemmell, July 2010.

Solar car park outside Palau Parliament House. Photos by Angus Gemmell, July 2010.

Solar powered car park outside the capital building in the Republic of Palau, northwest Pacific Ocean. Pictures taken by Angus Gemmell, July 2010

Envision Solar SolarPark

Solar Carport by Solar House Systems

Mock-up of solar carports to be installed in Southern California

Solar Carport--Carport Structures Corporation, Michigan

Kikukawa Solar Carport (Type 2)

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Resources and Links:

Carport Structures Corporation: “Solar Carports”

Cleanenergyauthority.com: “Southern California Edison to purchase power from new solar carports”

Kikukawa Kogyo: “Projects: K Solar Carport Type 2”

Newenergyworldnetwork.com: “Solar car park array becomes Saudi’s largest solar venture”

Solar House Systems: “SHS Solar Carpark with 13.8kWp sunpower modules”

Yourindustrynews.com: “Distributed Sun delivers solar power to Hilton Hotel BWI Airport”

Related previous Solar Choice Blogs: Building-Integrated Photovoltaics : Renewable energy in transportation/Electric Vehicle : Australian incentive schemes for solar power

Building-integrated photovoltaics (BIPV) is exactly what the name indicates: solar power generation modules that are integrated directly into a building in the place of ordinary building materials. BIPV differs in a number of ways from the PV arrays that most of us are familiar with: the roof-mounted or rack-mounted PV arrays that are retrofitted onto homes and produce electricity for domestic consumption or to be fed into the electricity grid. These bulky, rectangular structures usually made of mono- or poly-crystalline cells are what most of us imagine when we think of solar power because these are by far the most tried-and-true and therefore most common and trusted forms of solar power generation. This article explains in more detail what BIPV is and discusses the future trajectory of the photovoltaics industry towards increasing uptake of BIPV.

Conventional Solar PV Panels: A bit of background

As Mike Tomassi, International Business Development Director of System Photonics explained in a talk he gave at the Solar in Building Design and Construction (SBDC) Conference held in London 24 Sept 2010, the solar modules that we think of as ‘conventional’ were never intended to be used as building components. Instead, they have been designed for power conversion efficiency and price-competitiveness. Fortunately, their sturdiness and modularity, plus the industry’s history and experience working with them, means that these modules can be retrofitted onto older homes with relative ease and significant confidence that they will function properly. Nevertheless, it would be difficult to find proponents of these panels for their aesthetics. In fact, one of the main criticisms ordinarily leveled against solar panels (by architects, at least) is their unsightly appearance. On top of their visually unappealing nature, a number of functional issues make them less than ideal: they are difficult to make waterproof, they aren’t designed to be self-cleaning, and most of them were not manufactured with the idea of future recycling in mind. Future advances in the solar power industry will deal with these issues and ensure that modules can be smoothly integrated into design and construction: BIPV.

What, then, are the criteria for PV cells to be considered BIPV instead of conventional solar panels? Mike Tommasi uses France as an example of a country with simple, intuitive yet stringent requirements: in order to access the most generous feed-in tariff there, BIPV modules must meet the standards for and perfectly serve the function of the part of the building that they are meant to replace. If a module is designed to be a roof tile, for example, then when it is removed, the roof should leak when it rains. The purpose of a roof tile, after all, is to keep the rain out. It should also meet all the other requirements and standards that roof tiles are ordinarily subject to: they must be durable and resistant to wind, they should prevent the accumulation of dirt, and they should be ‘walkable’ so that that ordinary roof maintenance can be carried out when needed. If all of these criteria are not met, then the module fails to be good rooftop BIPV.

Given these requirements for functional flexibility, and the fact that in many cases BIPV is used for parts of a building which may not be ideally situated for full solar irradiation, it is not a surprise that this is where amorphous/thin film PV, is more malleable and less subject to inefficiencies due to shading and heating, comes into its own. Many of the technologies discussed here utilise amorphous PV for this reason. (For further reading on BIPV applications of amorphous solar panels, please refer to Miwa Tominaga’s Master’s Dissertation in the references section at the bottom of this article.)

BIPV: Energy efficiency teams up with energy generation

Renewable energy only makes sense when paired with energy efficiency. The recent 200 or so years’ abundance of fossil fuels has made power generation cheap and plentiful, leaving significant room for improvement in terms of how we use our energy. It is often said that energy efficiency is the ‘low-hanging fruit‘ of tactics for decreasing global reliance on fossil fuels. There are plenty of ways to take better advantage of the energy resources that are available. One of the greatest yet currently underused toolboxes available to designers and architects is passive design–design that focuses on creating site- and climate-appropriate buildings that use the energy resources that are readily available at the building site, such as the varying sun angle and prevailing winds, thereby mitigating the need for artificial heating/cooling demand and energy. Passive design techniques are generally relatively simple means to achieve these ends. A common example would be awnings precisely angled to allow sunlight into a building to heat it during winter but block it out when it would result in unwanted heating during the hotter months. Constructing such an awning using PV cells would kill two birds with one stone! This is why passive solar design and BIPV are already criteria in the LEED (Leadership Energy and Environmental Design) and BREEAM Green Building rating schemes.

Elements of passive solar design. (Source: Energysavers.gov)

This kind of ‘outside-the-box’ but eminently sensible thinking with regard to solar power will help PV on its march toward grid-parity. As most of the SBDC Conference speakers were keen to point out, solar power modules that perform multiple functions or that replace other materials in a structure will save on the cost of construction, even if the cost of using the PV-capable replacements is higher than the conventional materials. The Solarseeds blog refers to a comment by Dr. Douglas Dudis, a researcher with the US Air Force Research Laboratory, Materials and Manufacturing Directorate, who at the ASES (American Solar Energy Society) 2007 Solar Conference stated that, along with material availability issues and high labour requirements involved in PV technology manufacturing, a major factor contributing to PV’s relative unaffordable nature compared to conventional energy sources was lack of building integration. So the next question is, in what ways can integration happen?

Forms of BIPV

Roof tiles and shingles

Conventional solar panels are commonly retrofitted onto the roofs of homes and other buildings at an added expense: they require special mounting brackets and expertise. One of the easiest places to begin for a broad-scale implementation of BIPV is in ceramic or clay roof tiles, which are rigid, and asphalt shingles, which are flexible. 3-S Photovoltaics, a German company whose managing director Christian Renken gave a talk at the SBDC Conference, has developed a range of tile-type modules that are frameless, of regular size, can be installed by any roofer, and can be interspersed with tiles of the same size but different functionality, such as thermal collectors and skylights, as well as standard roof tiles. Similarly, Uni-Solar has manufactures a Power Shingle(TM) that can be seamlessly integrated into shingled roofs, secured in the same way that traditional shingles are secured–using nails.

3-S Photovoltaic Roof slate frame

3S Photovoltaic roof slates on a house

Uni-Solar PowerShingles(TM)

These are just two examples of what is available on the European and American roof-integrated solar power generation markets at the moment. Similar panels from other manufacturers have also come into production, as a quick Google search for ‘BIPV solar tiles’ or ‘BIPV solar shingles’ will give you some idea of what is available. One product similar to PV shingles and tiles on the market is PV laminates–thin-film PV that can be attached to the surface of parts of buildings, including roofs. Its superficial nature, however, may exclude it from the definition from the definition of BIPV outlined in the previous section–it is usually bonded on after the fact. Laminates are extremely versatile, however, which makes them ideal for retrofitting.

Solar facades, curtains, awnings, and windows

Another way that photovoltaics can be integrated into a building is in the walls of the building itself, or sometimes more effectively, in a multi-purpose ‘skin’ or curtain that surrounds the ‘core’ building inside of it. As with all BIPV, here too the solar cells serve a dual purpose. As Ray Noble pointed out in his presentation for the SBDC Conference, if the PV modules are price-competitive with conventional building materials and are intelligently crafted into the building design, then it is not imperative for the cells to have optimum orientation–any direction besides the poleward direction (north or south, depending on your hemisphere) will generate electricity with up to 90% the rated efficiency. In other words, it is not absolutely necessary that modules be placed on the roof.

There are a few options available in determining what to do with your PV in sections of the building besides the roof. These are roughly explained below. How their installation is implemented depends on the sensibility of the designer.

-Integrate into the walls. Perfectly vertical walls, of course, do not receive the same solar radiation the way slanted or horizontal roofs do, but they do receive some, especially if the building is located in the higher latitudes, where the winter sun comes in at low angles. ‘Perforated’ modules are available that will capture a portion of light for electricity production in the cells, while simultaneously allowing some light to transfuse into the building.

-Integrate the modules into a building’s surrounding ‘skin’. Some buildings incorporate such a skin for aesthetic as well as for climate control purposes. If the panels were, much like windows, capable of opening and closing, they could play a direct role in controlling the climate of the building, while at the same time having enough space to keep cool and therefore function efficiently

Norwegian University of Science and Technology: PV Glazing on Facade

-Solar awnings, as discussed previously, are advantageous in that they can keep the unwanted direct rays of the sun out of your eyes while absorbing them to create electricity. The angle of awnings could potentially be adjusted to best capture/block the rays of the sun depending on the season.

3S Photovoltaic sun shades: an example of PV for power and passive solar

PV Awnings could be placed over windows to provide shading and power

-Solar windows (PV glazing) and skylights serve the same purpose as their ordinary counterparts–to let in light, reduce glare (if they are tinted), and to act as insulation for or means of providing ventilation within a building.

PV glazing on German office building front windows

PV glazing on skylight in a German building

Some of the most fascinating and innovative techniques for passive solar are under development for the non-roof building parts mentioned above. Simone Giostra, founding partner of Simone Giostra & Partners and one of the other speaker at the SBDC Conference, referred to some of the technologies now under development as akin to science fiction: precision of an unprecedented level to integrate PV cells into the facades of buildings, increasing cell density where sunlight is expected to fall most intensely, decrease it where sunlight is expected to be sparser. This would enable optimum capture of solar energy for both electricity generation and lighting/climate purposes. Whether doing something so complicated is practical or cost-effective or not is at present questionable, but that the technology is being developed is praiseworthy.

BIPV vs Conventional PV in a nutshell

Provided that the cost of the newer BIPV technologies continues to fall, and that the building under consideration has yet to be built or is going to be a major renovation, BIPV will most likely be the first, most obvious choice for the designer/architect. Conventional PV panels win out where the building is older and the installation is a retrofit, and where price is a consideration. That being said, the BIPV technology that is most likely to take off in the retrofit market is BIPV roofing–especially on homes that need roof replacements anyhow.

The following is a summary of the Pros and Cons of BIPV and conventional solar PV.

Conventional ‘panel’ PV:

+Relatively commonplace throughout the world, including in Australia, and therefore plenty of infrastructure

+Durable and time-tested–will continue to function at more or less rated capacity for up to 25 or 30 years

+Industry standards have been developed and are well-known to experienced installers

+Efficiency of panels has been steadily increasing while the price has been decreasing

+Can easily be installed on top of a roof on a building that does not require any structural overhaul

-Big, rectangular, visually unappealing (to some people! I suppose this is a matter of taste…)

-Does not ‘add-value’ to a home’s functionality besides electricity production

-Placement options are limited–generally either on top of a roof or possibly ground-mounted

BIPV:

+Value-added! Well-designed BIPV generates electricity while improving the climate performance of your home/building

+Can replace almost all external building materials and thereby reduce the long-term over-all costs of a building via operational cost savings and reduced embodied energy

+Aesthetically pleasing–can be seamlessly integrated into the building envelope to give a sleek, modern look to a building (e.g. some of the pictures that accompany this blog entry!)

-Smaller market, many technologies are still under development and are not price-competitive on the retail scale with conventional panels

-Infrastructure, standards not in place, expertise needs to be built up (in Australia, among other places outside the EU)

-If some forms of amorphous PV are used in building, the productivity of the PV may decline in as little as 10 years–amorphous generally has a life span that is shorter than crystalline PV

The standard for solar power in the EU, the future of solar power for the world?

As discussed in this article, the importance of BIPV in architecture will continue to increase in the future. According to two articles from Solarserver.com and Renewableenergyworld.com, the future for the BIPV market is bright. Consulting group Frost and Sullivan predict that it will expand 108% by 2016 , reaching a worth of 2.7 billion dollars. The growth is attributable in large part to the generous and strategic financial incentive mechanisms in place in the EU for renewable energy, including feed-in tariffs and tax incentives. As with conventional PV, the the ultimate aim of these incentives is to accelerate the growth of the industry, eventually bringing PV-generated electricity prices closer to those produced by traditional sources such as coal, but without the negative side effects. Once the holy grail of grid-parity is achieved, BIPV will likely come to be seen as standard practice when it comes to new construction and major renovations.

Addendum: In another industry analysis report discussed in an article on Enhanced Online News, Market Research Consulting Firm Pike Research has projected that the worldwide BIPV market will grow to $4b by 2016, with the price per Watt becoming as low as $2.50.

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Sources and Links:

3-S Photovoltaics homepage

ASES homepage

Australian Government: Your Home Technical Manual (BIPV)

Energysavers.gov: “Five elements of passive solar home design”

PV Resources.com: BIPV

PV Glazing (solar windows) photos from ECW.org

Solar in Building Design and Construction (Based on notes from the 24 September 2010 Solar in Building Design and Construction Conference)

Solarseeds.blogspot.com: Building-integrated photovoltaics

Solarserver.com: “Frost and Sullivan project European BIPV market to reach EUR 2.70 billion in 2016″

Renewableenergyworld.com: BIPV Market in Europe Showing growth

Todaysfacilitiesmanager.com: “The state of Solar Photovoltaics”. (Top image also from this site)

Miwa Tominaga: “Opportunities for thin film photovoltaics in Building Integrated Photovoltaics (BIPV) with a focus on Australia” (pdf), Dissertation for Master of Science in Renewable Energy School of Energy and Engineering, Murdoch University, 2009.

Treehugger.com, “New Solar Photovoltaic Window System Announced by RSi Solar”

Uni-Solar homepage (Power Shingle(TM) photos from this site)

Previous Solar Choice blog entries: Asbestos in my roof! Can I install solar panels? (solar panel awnings) : Feed-in Tariffs : Which type of solar panel suits your needs?

On our blog we often receive comments from people who have installed solar power systems but, for some reason or other, are not seeing the optimal or anticipated performance from their system. Although the best approach in such a case is usually to contact your installer and ask for advice (especially if your system is new!), there is a short-list of likely problem areas that you may be able to investigate and remediate on your own, saving you the bother (and possibly the cost) of having your installer come out and have a look.

Solar power system problem diagnosis starts with your system type

Diagnosing any problem with sub-optimal power production begins of course with the question: What kind of system have you got? Specifically speaking, have you got a grid-connected or off-grid system? The follow-up questions you will need to ask yourself will differ depending on your answer to this question. This entry deals primarily with grid-connected systems, however, as most troubleshooting techniques can be applied to both types of systems. The biggest difference is that off-grid systems have batteries and battery-associated components and therefore tend to have more places where things may go awry. Keep an eye on our blog for an entry dealing with off-grid/battery troubleshooting to be written sometime in the near future.

What’s your problem?

Let’s imagine a few different scenarios:

1. Your system has not been producing at the anticipated Wattage right from the outset. By this, I mean that your system is either consistently putting out less-than-expected power throughout the day, or your system is only producing at capacity at certain times of day and the rest of the time is producing less. A typical complaint would be something along the lines of: “My installer told me I would generate 20kWh a day, but I’m only getting 5kWh per day!” Since your system is new and most likely still under warranty, the solution here is easy: your best bet is to ring up your installer and ask for assistance. They will know best how to handle the situation, and in any in any case are probably obligated to do so under whatever agreement you have with them.

2. Your system was working fine when suddenly and for no apparent reason there was a regular and persistent drop in power production, either throughout the day or for part of the day. You’ve had your system for a while and it may no longer be under warranty, and you want to see what you can take care of on your own. The first thing you should do in this case is dig up and dust off the maintenance manual that you should have been given when you had your system installed. There should be a troubleshooting guide contained within its pages. If you’ve managed to somehow lose your manual, your manual contains no troubleshooting guide, or you never had a manual in the first place, the steps detailed below will provide you a general guide to DIY maintenance.

Solar power system troubleshooting: Appliances, shading from neighboring objects, cables, panels

Appliances: Could the drop in power just be because I’m using more electricity?

The first thing you, as a wise system owner, will do is think hard as to whether you or someone in your home has recently started using any new electronic devices that may be increasing your energy demand. Next you might want to check and see if any of your devices, especially one that is on pretty much all the time such as a refrigerator, hasn’t suddenly malfunctioned and begun sucking up more power than it’s meant to. If you have a good monitoring system for your panels, you should be able to see this clearly, and if it is indeed the case, well, you’ve just saved yourself a lot of time and effort troubleshooting the rest of the system. If you can rule this possibility out, then you might need to consider some of the system components.

Immediate or nearby shading

You’ve been monitoring your system and one day noticed that they’re not producing the amount of power you expect them to. Your ability to monitor your individual panels will depend on your system configuration.

If you have a multiple-inverter setup (not so common in residential systems) you may be able to monitor each individual panel or each ‘string’ of panels. Generally speaking, however, most residential systems are designed with only one inverter, which means that you are only able to monitor all of the panels as a single unit, without the precision that a multiple-inverter set up might allow you. In this situation it’s more difficult to narrow down where the panels could be having problems, so there’s a bit more work involved. Let’s start with the most obvious potential issues: shading (in all but amorphous PV arrays) and heat fade, which is caused by excessive heat.

Shading can occur as a result of something actually on top of your array, such as a leaf, a pesky vine, or a rogue plastic bag, that blocks sunlight. This problem is easy to remedy: remove the offending object and see if your performance goes back to normal! (While you’re at it, you may want to give your panels a good washing”whilst the effect is not as dramatic as more blatant shading, accumulated dirt can affect panel productivity by 5-10%.)

The more insidious and intractable form of shading is that which comes from surrounding objects: trees that have grown tall enough to come between your panels and the sun for part of all of the day, or structures that have recently gone up around your property. If this is the sort of problem that your system is encountering, it should be fairly obvious, because your system may only be affected at certain times of day or certain times of year. It may be impractical to sit on a perch and monitor your panels during all sunlight hours throughout the year to check to see if shading is indeed occurring, but you should be able to pick out any likely shade-casting objects in the vicinity. You also have the option of visiting a site like NearMap.com, which can show you how your address is affected by nearby shading year-round. Although NearMap will not enable you to see shading throughout the day, it will allow you to pick out generally where the shading may be coming from throughout the year. Or you could check the problem yourself by simply waiting for the power to drop off, and then go out and have a look at your panels to see if there is some shading happening.

…or is your problem in the system itself?

A word of warning: Whilst it is true that you can do some of the troubleshooting yourself, a solar power system, no matter how small, is a live electricity production unit. There are certain parts of the system, especially the wiring, that if handled inappropriately or while connected can result in injury or even death. The last thing you want to do is become a casualty of your own ignorance of electronic circuits. So, if you do not know exactly what you are doing, consult a professional electrician or a certified photovoltaic (PV) system installer to do it for you or give you specific advice. Likewise, climbing up onto your roof to inspect your panels carries a similar risk. Use the utmost care or consult a professional. At the end of the day you’re better off with a lighter wallet than in hospital or the morgue.

Well then! If you haven’t been frightened off by the dire warnings, let’s start troubleshooting with the components common to both grid-connected and off-grid systems, then: wiring, panels, and inverters. Then we’ll look at the components specific to off-grid systems: batteries and charges/charge-regulators.

Faulty wiring or panels in a solar power system

Conducting selective shading test

If you suspect that a solar panel itself or its wiring is causing problems for you, there is a simple procedure that works especially well with mono- or poly-crystalline panels (amorphous panels are not as vulnerable to shading effects) that you can perform to test your hypothesis: the selective shading test. If you have a parallel or series-parallel array configuration, this test will help you determine which panel or which series is the culprit. This is because the voltage of your system is relatively constant, regardless of shading, while the current is greatly affected by even partial shading. Voltage increases when you line up panels in series, but current increases when you put panels (or a series of panels) in parallel with one another. If you only have one series of panels in your array, however, the shading test may only tell you whether there is a shading problem, not where it might be. (For an explanation of the difference between current and voltage, read this previous blog article. The rules of current and voltage also apply to batteries. You can read about how battery banks are designed in this previous article.)

So how does one conduct this test? Well, shading even just a few cells in a mono- or poly-crystalline array will result in a significant and sudden decrease in output; shading even just 4 cells should result in a drop of more than half the output of a panel or string. With the array connected and working, monitor the output while you shade the panels. If there is NOT a significant drop in output when you shade the panels in full sunlight, you have found your faulty panel/panel series. The next step is to figure out what part of the system this could be originating from.

The effects of heat fade on your solar system

Another reason you are experiencing a loss in productivity might be that your panels are too hot, resulting in a phenomenon called ‘heat-fade’, where your voltage drops. This is especially likely to happen if you have a weak cell somewhere in your array. Panel performance is usually calibrated at a test condition temperature of 25C (Standard Test Conditions or STC), and operating above this temperature results in generation losses. Your installer should have taken the effects of heat into account when considering the Normal Operating Temperature and Conditions (NOTC), the actual expected temperature range on the ground where you are. The expected reduction of output in volts per degree of temperature above the STC temperature should be provided in the specifications of the brand and make of panel you have installed. (Incidentally, heat actually has an insignificant but positive effect on current; however, this is greatly offset by the voltage and therefore overall associated power losses.)

Some reduction in capacity is to be expected with heat gains, and your installer may have told you how much power production to expect at a certain temperature. You can check if your system is being adversely affected by the heat by cooling your panels with water and observing the system output to see if there is a significant change. When so cooled, does it rise to normal output levels? If so, you need to determine where the weak link is. You can do this by disconnecting the panels in your array and checking their open circuit voltage (Voc), which, in a nominal 12V array, should be about 18V (All depending on the specifications of your panels! This number will increase proportionally with higher-voltage systems; e.g. a nominal 24V system would have a Voc of about 36V). If your Voc is less than you’d expect it to be, then either a portion or the whole of your system has a problem. You can go back and conduct a shading test as described above to try to find the faulty bit.

Checking for faults in the wiring and connections in your solar power system

If neither of the two above tests reveals to you where your problem may lie, your power loss may be occurring somewhere in the balance of system (BOS), however–wires and connections are a prime suspect, and if you have an off-grid system, you’ll need to investigate your batteries.

1. Check your wiring or have it checked by someone who knows your system

Solar panels themselves tend to be fairly dependable: because they have no moving parts there’s little than can go wrong with them mechanically. If you’ve ruled out the potential of panel-related problems, you’d be smart to look at your wiring, as this is often where problems occur in a system.

A. If you find yourself suffering from a total loss of power (in grid-connected systems you won’t actually be subject to a blackout, but you should notice the lack of production by looking at your meter/monitor), the first place you’ll want to go is your circuit board. Have any of the fuses blown? Try switching them back on if they have, and keep an eye on them to make sure that it doesn’t happen again. If it does, there’s something happening in your system that is causing the circuit to blow out. This could be a faulty connection, or a component may have gone haywire. Hopefully your circuit board is labeled clearly so you know which circuit is having the problem, enabling you to narrow down the likely culprits.

B. Loose or totally disconnected cables will result in partial/sporadic or total loss of power, respectively. Check all the connections to see if anything is obviously amiss–a wire is hanging loose or barely connected. Don’t attempt to fix it yourself unless you are certified to do so,  you know exactly how your system functions, and you know for an absolute fact that there is no electricity coursing through the system. Even if you can’t do it yourself, at least you’ll be able to rest at some ease knowing where your problem lies, and call someone to fix it with confidence.

-The problem of corroded connections is especially common with older systems, as oxidisation of exposed metals happens naturally with the passing of time. The easiest solution is to clean any corroded bits first and check that the connections are tight. If this is where your problem is originating, you should be able to see your power come back after you’ve done this. But again: this should only be attempted if you are certified to do so. Playing with wires is risky business.

-If the problem persists but the connections all seem to be corrosion-free and snugly connected and that all the soldering is in properly in place, and you’re certified to do so, you might go through each connection and check with a voltmeter in order to try to find cables that have stopped conducting electricity. This problem is highly unlikely, however, unless you are aware of an incident, such as a cyclone or tornado or car/building accident, that could have compromised the integrity of your cables. In any case, checking some of the connections might be tricky, especially the ones underneath your panels. If all the accessible connections seem to be checking out all right, you can move on to troubleshooting the panels themselves.

How about my inverter?

It’s also possible that your inverter may be oversized or undersized, but if this is the case, you should have been aware of this issue from the outset of having your system installed. You can read more about the importance and effects of inverter sizing in this previous blog entry.

But the best medicine is preventative

Especially in the case of problems with wire connections, the best strategy is to be proactive in looking for potential problems with your system, keeping a regular log of its function and noting if anything seems amiss. This is especially true in an off-grid system, but also important in grid-connected systems. The earlier you notice and deal with a problem, the more likely it is that you’ll be able to take care of it quickly and avoid losses, saving or possibly making you money!

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Resources and Links:

Previous Solar Choice Blogs: Stand-alone system battery maintenance : Types of photovoltaic panels : AC vs DC electricity : How to size a battery bank : Solar Choice FAQs

Ground-mounted solar photovoltaic (PV) systems are ideal for those who have space to spare on their property. The are becoming increasingly common. In fact, there is a movement to recruit solar farmers, who, taking advantage of generous feed-in tariffs and solar rebate incentives, would be able to turn a profit from otherwise unproductive land. This article focuses on one technology for mounting solar systems: ground-screws.

One of the issues with ground-mounted PV systems is the labour-intensiveness of their installation. Preparatory ground excavation and construction of concrete slabs is often necessary, as the panels need to be stable enough to withstand storm-force winds. Ground-screws are one viable alternative to these concrete slab-based mounting systems, offering comparable sturdiness at potentially reduced cost. Essentially, this is one more option for you to consider when planning how to go about your solar power system!

What are some of the advantages of ground-screws for mounting solar photovoltaic systems?

-Usually less invasive and landscape-altering than traditional mounting systems such as the half A-frames that are typically installed on cement slabs (described here in more detail)

-Screws can be easily adjusted to less serious gradients so mounting-frames are installed level: less complicated earthwork and engineering involved as compared to cement slabs

-More aesthetically pleasing than a cement mounting platform: shade-tolerant grasses and plants can easily grown beneath them

What are some of the disadvantages of ground-screws for mounting solar PV systems?

-Ground-screws cannot be installed in all types of soil: some soils are less stable than other, and large rocks can be an issue

-Land with steep gradients may still require earthworks: ground-screws only go so deep

Solar Choice and solar systems using ground-screws

Solar Choice has overseen the tenders for a number of ground-mounted solar PV system installations (photos can be seen below) utilising Krinners ground-screws. Krinners produces and handles the planting of ground-screws for various applications, including solar power systems, football goal-posts and fence-posts. We have a good working relationship with Krinners and are able to advise you as to whether their services may appropriate for your solar power system.

Sunshine Coast: 30kW PV Solar Choice customer–system to be mounted on ground-screws

As you can see, due to the steep gradient on the site, this installation had required some preliminary earthwork.

Dungog, NSW: 10kW Solar Choice customer–system mounted on ground-screws

Here, no preliminary earthwork was required. (Photo at top of article also from this site.)

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Sources and links:

Krinner Ground-screws website

Previous relevant solar choice blog entries: Ground-mounted PV systems : Solar farming opportunities : Solar Feed-in tariffs : Renewable Energy Certificates (RECs)

You are now mentally and financially prepared and willing to go ahead with a solar panel (photovoltaic) installation on the roof of your home. The only problem is, after having your potential installer come out and have a look at it, you’ve found out that your roof has got asbestos in it and your installer has reluctantly informed you that they will be unable to carry out the install. Where can you turn? Fear not! There are potentially a few other choices available to you.

Asbestos fiber, until a few decades ago a common component in buildings as a fire retardant and noise insulator, can have serious negative health repercussions for those who work with it. It can crumble and decay over time, and can then be inhaled as it floats around invisible in the air. Agitation or removal can induce its disintegration, and a common tactic for dealing with it when it is discovered is to not touch it at all, or to contain it as it is. It’s no surprise, therefore, that an installer might not be particularly keen to start drilling holes into an asbestos-laden roof.

So what are your options?

-If your solar installer agrees to do the install if you get rid of the asbestos, you could look into having it removed professionally, thereby clearing the way for construction. Make sure that the remover is reputable and professional–asbestos removal is not a job to be undertaken lightly.

-More likely, however, it would be wise to find an alternative spot on your roof, or the roof of another building on your property (e.g. a garage) with a north-facing aspect. By doing so you may be able to avoid the asbestos issue entirely and still stand to reap the benefits of solar power, potentially even if the new roof you have selected is in a sub-optimal location. You can contact a Solar Choice broker directly, or ring us on 1300 78 72 73 for detailed regarding your options for placement

-If you own a large property with sufficient space to do so, you could consider a ground-mounted installation near your home.

-It may also be possible to install photovoltaic panel awnings above your windows or doors (such as can be seen here and in the image at top). Depending on the aspect of your building and space available on walls, this would actually enable you to choose an optimal tilt angle for direct insolation (sunlight) appropriate to your location. Additionally, awnings may also serve the secondary purpose of keeping direct sunlight out of your home, thereby helping to improve the visual and climatic comfort for people inside.

Written by James Martin

Solar Choice Analyst

© 2010 Solar Choice Pty Ltd

Sources and Links:

Worker’s Health: Asbestos Factsheet

Thanks to the Greenwala.com Tech blog for the top image.