As part of Transition St Marys we are looking at bulk purchasing to help each other out by increasing our buying power and negotiating discounts from suppliers. One thing we are looking at is bulk purchasing solar power systems. Here is an example of a successful scheme: http://www.goldfieldssolarhub.org.au/
Some ideas so far are:
- The buyer pays the supplier direct, this solves the problem of having to hold large sums of money.
- The systems offered need to be in different sizes to suit the different budgets. That we way we potentially get more people involved.
- No local government involvement, this was unanimous at or first meeting, we want to be independent.
- We could approach suppliers for quotes for systems based on different numbers of buyers, ie 20 systems or 30 etc, and when it is fully subscribed then close that round.
- What geographic region do we take in, just Break O’Day or neighbouring local govt areas?
- The group will organise the buyers and get quotes, then the supplier will bill each purchaser individually and arrange installation directly with them.
The next step is to write to suppliers and gauge their interest and get an overview of prices and their service offers.
As part of this overall process I have prepared the following to help those that are not familiar with solar systems so they can understand a bit more about what to expect and avoid some pitfalls. This summary contains a few key points to consider when planning a solar system. Hopefully in plain English. It pays to learn some of the lingo and understand a little more what the salesperson is on about. Our last supplier told a few porkpies, so it is best to be armed with some understanding before you start.
It may sound confusing but there is always the option of paying an accredited installer to design your system for you. At the end of this article there are a few questions to ask when looking for a suitable system to make sure you get the most for your money.
A Stand Alone System simply means that you generate your own power and do not connect to the Aurora grid. You store your excess power in batteries and draw it back from the batteries at night. A Grid Connected System means you still generate your own power but the excess goes into the Aurora grid, and at night you draw it back again.
Stand alone systems have a minimum of three components, Solar Panels, Voltage Regulator and Batteries. I’ll explain what these are later. This type of system provides 12v DC power. If you add in an Inverter this makes the 12v into 240v, which is the same voltage used in houses attached to the Aurora grid. Here at Banksia Hollow we intend to be off-the-grid as that best suits our values and beliefs. We had solar power at our last house and it was just amazing to watch the panels just sit there and provide all our energy needs. There is 1000w of energy beaming down on every square metre of the earth. Why are we burning coal and paying interest on huge infrastructure projects when this stuff is free once you buy your system and it can last potentially 40 years with very little maintenance.
Small Scale Technology Certificates (STCs) are available for every system installed. Most people cash these in with the supplier at the time of installation to make their system less expensive. They do have a value, a bit like shares, and can be kept as an investment and sold later if you choose.
The two most common types of solar panel are Mono-crystalline and Poly-crystalline. Mono-crystalline is the most efficient at 18%, followed by poly-crystalline at 16% but of course Mono-crystalline is usually more expensive.
If a small part of a panel becomes shaded then the panel will shut down. To avoid this panels need to have Bypass Diodes in them so that they do not totally lose their efficiency if partially shaded. The more bypass diodes the more shade tolerant the panels.
Sun Trackers move the panels to follow the sun. They are expensive and make the panels more vulnerable to high winds due to the single pivot points. Also by introducing moving parts it increases the likelihood that more maintenance will be required in the future.
It is best to have panels that can be tilted at different angles as this can add 14% to the output of the panels. For St Marys/St Helens the optimum angles are Winter 64.5°, Spring and Autumn 41° and Summer 17.5°. This can be achieved by modifying the backstays by drilling holes for each tilt point and manually tilting the panels. It is good to have some air circulating behind panels as their efficiency drops right off at 70° Celcius.
The panels themselves do not emit any EMFs, they need to be cleaned once a year and you may need to fit rubber spikes if birds keep landing on them and leaving deposits which obscure the surface. You need to bear in mind where you are installing the panels so you can gain access to clean them, and if you want to get up on the roof and change the tilt angle you need to make sure it is safe to do so. Of course you can just leave the panels as installed without tilting them, this just means that you are not getting the most from your system but that is OK too.
You can add and mix and match solar panels but you cannot run old and new batteries together, generally if you are running off grid you will need to replace all the batteries at the same time which is OK as if one goes the others will not be far behind anyway.
Lead acid batteries are the cheapest suitable batteries and they come in two types, wet cell and dry cell. Dry cell are also known as sealed gel batteries. Deep cycle batteries are the best as they last longer. Ordinary car batteries (wet cell) can be used but they are not deep cycle so will not last as long. Good quality batteries should last 15 years or so. Batteries can cause an explosion hazard caused by gassing if they are not installed and regulated correctly.
Inverters (the box that changes 12v to 240v) come in two types, grid-connected and stand-alone. You can’t connect a stand-alone inverter to the grid, and vice versa. So make sure you buy the right one for the system you are planning. Sine Wave inverters are the best. Modified Square Wave inverters come in second, and you don’t want a simple Square Wave inverter as it may bugger your appliances. If you are desperate to know more about the types of wave form, that’s why God invented Google, so go for it. It is best to buy an inverter that has protection against thermal overload so that if it gets too hot it disables itself. Reverse polarity protection is another good feature to have so that the device isn’t destroyed if it is accidentally wired incorrectly.
Inverters should be capable of operating in standby mode. This is because inverters use electricity to operate so it is important that they can shut down into standby mode when not in use. If your system is off grid it is important that the appliances you connect to your system do not constantly draw current on standby, ie a TV on standby, as this will prevent the inverter from going to sleep and it will keep running and draw power from your system. Also be aware that Inverters emit EMFs and usually have a warning printed on them. Make sure you don’t install it where someone sleeps behind the wall or somewhere that you spend a lot of time. The distance is fairly short but it is still something to consider.
The voltage regulator is the part of the system that makes sure the batteries are protected and provides the correct amount of flow in the system and protects the batteries from overcharging. Maximum Power Point Tracking (MPPT) Regulators are the best as they can provide up to 20% more current to the batteries but of course they are more expensive. Bear in mind that 20% more power may mean $700 less spent on panels so the extra expense for the regulator may be good value.
With solar systems there is a risk of electrocution and they need to be earthed and have circuit breakers fitted. You need to be licensed to install any part of a system that uses 240v but anyone can install 12v. It is important that it is done correctly, firstly for your safety and second to get the most out of it. So bearing this in mind you may want to learn more if you intend to install an off grid system yourself. There are courses available through Adult Education in Tasmania. The cost is around $140 for two days. I recently did a course through Adult Ed with Ian Smith and he provided excellent notes and used language that the uninitiated could understand.
Some questions to ask when looking at Solar Systems . . .
- What type of panels, are they mono-crystalline? If not, how efficient are they, and are they really cheaper if they are less efficient?
- Who keeps the Small Scale Technology Certificates (STCs)?
- Do the panels have any bypass diodes? How efficient are they in partial shade?
- Can the backstays be adjusted to tilt the panels?
- Is the voltage regulator of the maximum power point tracking (MPPT) type?
- If going off grid, are the batteries gel/sealed deep cycle batteries?
- Is the inverter sine wave or modified square wave?
- Does the inverter have standby mode?
Banksia Hollow 