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Solar Powered Stand Alone Power Systems: Ways to minimize cost!

There are several components to designing a Solar Powered stand alone power system and thus there are several ways to minimize the cost of the system! This article will talk about each component how it is sized and what your options are in each case.The average solar powered stand alone power system consists of the following components:

  • Solar Panels
  • Solar Controller
  • Batteries
  • Inverter
  • DC / AC Appliances

Each of these can be optimized to the resource available (the amount of energy seen by the panel) and if the resource is not enough things like maximum power point trackers and generators can be added to the system. This will add further complexities however in some cases can lead to reduction in the number of solar panels and size of battery if one has access to petrol/diesel for a generator.

Starting with the DC/AC Appliances:

It helps to buy products with low surge factors, this is something that you should be able to ask about when you purchase the product from a store. If not, it is an answer that companies have to give consumers. Having low surge factor products in a home can allow you to have more appliances on at the same time or allow you to use a lower rated inverter. Using appliances that consume less electricity or have higher energy efficiency standards also allows you to save money on the battery bank and the array of solar panels because now you don’t need as much energy to be stored or generated.

The Inverter:

Buying a bigger inverter allows you to leave room for new appliances that you might not have thought you needed at the time of installation. Usually there is a safety factor that designers and installers use but it is not very large and contracts will usually suggest what items they have accounted for in their design thus it might be useful in the long run to chose a bigger inverter.

The battery pack:

A common piece of advice not followed in industry is the use of parallel battery banks. Unlike parallel solar module arrays this is a bad idea given the irregular charge and discharge cycles that residential usage forces on batteries. This means there is a greater decrease in the lifespan of the battery pack and increases in the cost of wiring the batteries, and if the wiring is not done correctly it increases the system losses and might be the reason for the installer adding one or two more batteries ‘just incase’.

Solar Controller or Maximum Power Point Tracker:

This is a tricky one to talk about without going into specific case studies and results. For the point of this article I can suggest that using a maximum power point tracker allows you to produce more power from your panels in low light conditions and in varying temperature. Thus using an MPPT can theoretically suggest the use of a lower number of modules but because the MPPT role is to regulate the charge flowing between the Solar Panel and the battery it would make more sense to down size the battery bank than to down size the modules, ensuring that your batteries are able to go back to full charge more often, a state of charge which is preferred in order to prolong the battery lifespan (especially because in most cases parallel battery banks are cheaper upfront than series battery banks).

Solar Panels:

There are two options here. Either oversize your modules so you won’t need a generator (usually in industry this is 1.3 times the load that needs to be provided based on the users consumption habits) or down size your panels and use a generator to charge the batteries for a certain number of hours a day, where a certain number of hours every month must be reserved for ‘equalizing’ the batteries.

Written by Prateek Chourdia

MEngSc – Photovoltaics and Solar Energy, UNSW

Solar Energy Analyst

Solar Choice

© 2010 Solar Choice Pty Ltd

Comments

  1. Hi! Stand Alone Power System can works well and generate power only when you get best solar power system installation service. I bought 3 years before this Stand Alone solar power system, But off grid connection is also not a bad choice. I am also thinking of buying it for better power supply.

  2. Hi, I have just spoken to Synergy, since I have solar power, Synergy tells me that now I need to invest in a new meter, so they can read this accuratly at my costs of being $275 for the meter itself. Then Synergy takes my grid at being $0.80 but if I need to buy this back of them say in winter, I pay over $0.22, ok where is the fair deal here? First I lash out over 10K to get this solar installed and Synergy- the onlt supplier in WA- rieks the benefits after they milked me for the meter costs. So my question is, I now rather look into a solar battery pack as it hurts me being ripped off, how much will this costs? As for now I disconnected my Synergy account, until justice will be done….

    1. Hi Silvie,

      Everyone who installs a solar PV system has to upgrade their meter to either a smart or bi-directional meter in order to be connected the grid. A good installer will advise you of this up front, indeed the price of grid connection is set out in the Solar Choice Solar Quote Comparison so people who use our service are aware of all the costs associated with installing a solar PV system.

      The cost you have been quoted for grid connection (the meter) is in line with what we would expect, so you are not being charged over the odds. Although the new feed-in tariff rates are frustrating for many customers installing after the Premium tariff has ended you should be benefitting from far lower system costs. The days of viewing a solar PV system as a means of making money are long gone, instead we advise customers to consider the value of the solar they produce in terms of what they do not need to buy from the grid. We also advise customers to find ways of consuming as much energy as possible when the panels are producing power, such as running washing machines during the day and turning the cooling system of their air conditioning off once their panels have stopped producing.

      Battery costs are not included in our standerd quotes as they roughly double the cost of your system. You should contact your installer for more details on price and installation costs for batteries as we do not currently hold details on this.

      We hope this feedback helps and good luck going off-grid if you decide to do so.

  3. Hello,

    I’ve been considering solar power for some time now, and would like to find out whether we have the option of installing a grid feed system that also provides me with the option of moving off grid onto a battery pack… Is this possible? what are the design / cost / rec implications etc.. I probably need somewhere between 2-4 KW system.

    Thanks

    1. Hi Gregory,

      Thanks for commenting.

      Ordinarily it is not possible to have a grid-connected solar system with a battery backup. In fact, if the grid ever goes down, grid-connected solar arrays are rendered non-operational for safety reasons. Most inverters are no ‘smart’ enough to feed electricity only into the house when the grid goes down.

      If this is what you are interested in doing, however, the best option would probably be to invest in an inverter technology such as the PowerRouter, which enables you to use some power from your panels even when the grid is down, and when expanded with a modular battery manager pack, enables a home to have a battery backup. This is beneficial for a number of reasons: you can save electricity to feed back into the grid at any time you’d like (good if you are on a solar feed-in tariff plan), plus the obvious advantage of having a back-up power supply for if the grid goes down and your solar array is not producing power (e.g. at night.)

      As far as incentive implications are concerned, there shouldn’t be any! Your system would be eligible for all the same incentives that a grid-connected system would be–Federal Solar Credits, and state-level Solar Feed-in Tariffs.

      Hope this has been helpful.

    1. Well it depends on a couple of things how much energy on average your household will consume given the appliances you will be using and then whether you want it to be totally solar powered or if you would like a diesel generator as back up?

      If you fill out the form I am sure one of our agents will give you a ring once we have your details so that we can have a formal discussion of what your needs are and how they can be best met. FORM

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