Earth Notes: Solar Powered Schools

Cuts bills and footprint, educates children, and makes good use of roof space!

Solar power and schools can be a good match in many ways: not just helping insulate their budgets from energy price rises, but also providing a basis for lots of maths and science around energy production and consumption in the West and developing countries, climate change and so on.

From involvement with charities such as SolarAid to making use of roof space to help wean themselves and the country off fossil-fuelled electricity and heat, schools can be beneficiaries of solar microgeneration in a number of ways.

King Athelstan Solar PV

I was very pleased in 2012 to help organise a PV system for King Athelstan Primary School, the local community school that both my children attend. I am quoted:

Solar power is good for the school, for the surrounding area, and for the planet: having solar power means that we can burn less gas and coal to make electricity for the country, leaving more for other important uses and reducing the threat of climate change. King Athelstan putting its roof to good use!

Even better, our local MP, Ed Davey, as Energy and Climate Change Secretary, was able to come and declare it officially 'open', which has the nice side effect of some good PR for the school!

King Athelstan's installation is solar PV, ie for electricity, and should cover about 10% of its current consumption over a year, and vastly reduce the need to import from the grid at all over the summer months especially during weekends and holidays.

Conservation remains important, and I hope that we can halve electricity (and gas use) or close to, by efficiency measures. That would have the effect of the PV then covering 20% of the remaining electricity consumption...

The red line on the chart shows electricity generation in kWh (units) per day.

The blue line shows approximately what percentage of the school's entire consumption that is.

The green line shows what fraction of the generation is from the "thin-film" panels; they are reputed to work relatively better than monocrystalline panels in cloudy/overcast weather, but keep an eye on the chart to see if that is actually borne out by experience. Note that when the sun is very low in winter shading from trees and so on may confuse the issue.

For other schools, eg residential establishments, a solar thermal system to contribute to hot water supply may also be useful for example.

A (prettier) snapshot of electricity use vs the first summer's generation (c/o EnergyDeck):

consumption and generation at KAPS

Educational Exhibits

I used to love all the exhibits at the Science Museum in London where I could push buttons and pull levers and so on as a kid. I'm hoping to put together some very simple exhibits King Athelstan and other local schools to use where kids can cover/uncover solar cells and watch meters twitch and motors whirr, for example. Hardly likely to greenwash the children, but may generate a little interest along with the Watts. I remember that my dad got me fascinated in electronics with stuff not very much more complex!

simple panel/LED/meter interactive exhibit

Solar Meter V1

2012/06/16: I'm putting together a very simple device with a small solar cell/panel (~4Voc, 0.25W) wired to a simple analog meter (Maplin LB08B 65Ω, 250µA FSD) with a series resistor to protect the meter in bright sunlight.

The cell and meter are in a clear plastic box stuck to opposite sides such that covering the cell with a hand has the meter drop back to zero if otherwise lit. To get FSD (full-scale deflection) at (say) V=2.5V implies a 10kΩ series resistor; the meter can probably stand 100% overcurrent for a while, so something close to this or a little higher is probably fine, while giving decent needle movement even if not in bright sun.

I've actually put a 3.3V white LED upstream of the meter, as a voltage limiter, with a further 470Ω to the solar +ve, so that if the light is really bright the LED comes on and limits the meter to FSD.

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