Solar PV systems convert sunlight into electricity
Solar electricity systems - also known as photovoltaic or PV systems – convert sunlight into electricity. Light energy (photons) hits solar panels, which are usually placed on a roof facing the sun. The photons excite the electrons in a semi-conducting material (such as silicon), producing an electric current.
Would solar PV suit your business?
Solar energy is free – but harnessing it requires investment. It may be a good match for your business if:
- it mostly uses electricity during the day
- it uses more electricity in summer
- you’re in your business for the long haul – it could take several years to get payback.
Most solar-powered business still need to buy electricity
Most New Zealand businesses with solar panels stay connected to the electricity grid. They purchase electricity from the grid when the solar system doesn’t generate enough electricity – like after dark.
Installing equipment for stand-alone power systems – such as a battery bank – means you can store electricity. Although battery prices are falling, it will increase the cost of the system significantly. Prices are expected to fall over time as more systems are installed and technology improves.
How much electricity can they generate?
Each solar PV panel is rated on its peak electrical output. For example, a panel with a 75 watt peak rating (75 Wp) will have an output of 75 watts under test conditions. On average, a well-placed panel produces the equivalent of full power for 2.5 to 5 hours per day. So a 1 kW panel can produce 2.5-5 kilowatt hours (kWh) a day, or between 912 kWh and 1825 kWh per year.
Building a business case
To work out the return on investment, you’ll need to dig into how much you pay for electricity – both the cost per kWh and the capacity cost. Weigh the cost of your investment in solar panels against the cost of buying from a retailer.
Tips on installation
Businesses usually install panels on building roofs but you can also place them on facades, conservatory roofs, sun shades, garages or specially-built stands on the ground.
The site should ideally:
- face north
- be free from shade and exposed to good sun all year
- have enough space - a typical 1 kW panel needs around 8 m2.
As a rule, your site will need will need 8m2 for a typical 1 kW unit. If you’re designing a stand-alone power system, you may need to combine your solar PV system with other generators, such as a small wind turbine, hydro system or biodiesel generator.
Solar thermal for outdoor pools
Outdoor swimming is a whole lot more comfortable with an efficient solar pool heating system. Black plastic solar panels are usually put on a nearby roof, such as a changing shed. High volumes of pool water are pumped through the panels and back into the pool, so the pool temperature gradually rises to a comfortable 28°C.
The system automatically switches off when the pool reaches 30°C. Using a pool cover overnight makes the system even more efficient, and reduces maintenance and chemical use.
Many schools have funded systems with the help of an interest-free Crown loan.