September, 2009
Aliens are probably laughing their tentacles off at our approach to energy generation. We spend our days fighting wars over a dwindling supply of black sludge, beneath our very own giant free fusion reactor.
Many homes in New Zealand have 20 – 30 times more solar energy hammering down on them each year than the owners use in electricity or gas. We have, at least, got as far as developing photovoltaic cells to convert this energy into electricity. But with the average Kiwi household using about 8 kWh of electricity per person per day, the Energy Efficiency and Conservation Authority calculates that to supply all the needs of an average family of four would require a system costing between $60,000 and $170,000.
So reducing power use remains the first priority if you want to save money and protect the environment. But the tantalising prospect is that if every New Zealand home had a 3kW photovoltaic solar panel array, they would generate enough power to satisfy more than a quarter of New Zealand’s residential electricity needs.
That would mean we could shut down the Huntly coal fired power station, assuming we didn’t need it to back up our renewable sources on those still winter evenings…
The dark side of the sun?
There’s no such thing as free electricity, either economically or environmentally.
The glass, plastic and metal fittings in PV systems take energy, water and a wide range of chemicals to make. Some of these are toxic or hazardous. PV modules also use palladium silver, nickel, nickel chromium or tin for metallic contacts and usually a tin/lead solder for electrical connections. Not to mention small amounts of cadmium, which is toxic and has a tendency to accumulate in the food chain.
The resulting cells are generally only good for about 20 years. And although the cells are more or less benign in use, disposal of dead cells is also problematic. Recycling programmes are being developed, and some manufacturers will take back old panels to recover the more valuable materials.
There are some other, unavoidable, limitations. Because PV cells only produce power during the day, and relatively little when it is cloudy, even the most super frugal electricity user will need some sort of backup if they don’t want to be left powerless from time to time.
Other renewable generation options like wind can help to iron out the peaks and troughs if you have the right conditions, but for most people off the grid, lead acid batteries containing sulphuric acid are the most useful option. Nickel-cadmium batteries are less common and much more expensive, but last longer. Depending on the system and how it is maintained, the batteries you use will last somewhere between 3-15 years.
As PV technology advances the costs are falling and the efficiency of the panels is increasing, making it a more viable option. However, as things stand, when you take into account the costs of installation and maintenance, and even once you have negotiated with your local energy company to sell power back to the grid, you will almost certainly be paying more for each watt of electricity than if you plugged into the mains. And whether your system adds its full value to the cost of your house depends on the temperament of the potential buyer.
While there are 100% renewable energy providers like Trustpower and Meridian around, even the overall environmental benefits of having your own PV system are difficult to quantify. But wind farms are a blot on the landscape, and there are benefits from reducing our hydropower use to reduce the pressure on our water systems. There’s no doubting the added self sufficiency and resilience provided by your own personal power generation. And if you can’t get on the grid, or don’t want to, PV is less polluting than gas.
The paperwork
Building or resource consents may be required for photovoltaic systems that penetrate the roof or are considered by neighbours to affect their property. Any grid-connected photovoltaic systems need to be agreed to by both the lines company (for the connection) and the electricity retailer (for pricing arrangements). And you need to get an installer who knows what they are doing as the system must meet the AS/NZS 3000:2007 electrical installations wiring rules.
Tags: green living, Innovation, solar power