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Solar Energy FAQ

By: Dr Gareth Evans - Updated: 2 Sep 2012 | comments*Discuss
 
Solar Energy Solar Panels Photovoltaic

Solar energy has a strong appeal and interest in it is growing by the day; below you'll find answers to some of the most frequently asked questions about solar heating and photovoltaic systems to help you decide for yourself if it seems right for you.

What’s the Difference Between the Two Different Types of Solar Energy Systems?

Solar panels heat water using the warmth of the sun and then transfer the heat collected to your domestic hot water system.

Photovoltaic (PV) systems are “solar cells” using the sun’s light to generate electricity for use in the home. It can also be exported to the grid if sufficient is produced.

Is My Home Suitable for Solar Energy?

The basic minimum requirements for both solar water heating and PV systems are much the same, calling for unobstructed exposure to the sun during the sunniest part of the day - typically between 9am and 3pm – and the opportunity to mount the panels or cells at an angle around 20-50 degrees to get the most benefit. A south-facing roof which enjoys direct sunlight during the two hours either side of noon is particularly ideal.

How Much Roof-Space Will it Take Up?

You’ll typically need to allow about 4 square metres of available roof-space for solar water heating panels, while a PV system will demand three or four times as big an area of roof.

How Much Does it Cost?

Installing solar water heating for the average home costs between £3,000 – £5,000; PV systems are generally more expensive, costing from around £4,000 to £9,000 or more.

How Much Energy Will it Save?

Solar panels should save around a third of the energy used for heating water; PV will generate around 750–800 kW hours of electricity annually.

Will I Need Loads of Batteries?

Not for solar water heating, but if you’re planning to have a PV installation that isn’t going to be connected to the grid, then yes, you’ll need to use batteries to store the power generated. Your installer or supplier should be able to advise you on the right sort for your system as well as the necessary additional equipment you’ll need to regulate the charging of them.

Do I Need Planning Permission?

Since April 2008, the need for planning permission has been removed from most micro-generation technologies in England, allowing them to be installed under the General Permitted Development provisions. There are still some occasions when planning permission will still be needed – if the panels will protrude more than 20cm or are in a Conservation Area and visible from the road, for example, so checking with your local council remains a good idea, though for most householders there will be no problem.

In Scotland, Wales and Northern Ireland, planning is a devolved issue; although similar legislation is coming into force, it is essential to check with the appropriate authority to stay on the right side of the relevant country’s law.

But What Happens When it’s Cloudy?

Obviously both PV and solar water heating work best when the sun shines, but even on cloudy days, all is not lost. When the sun does peep out from behind the clouds, there can often be enough heat to help warm the water, but there’s no escaping the fact that this sort of solar energy system really does need the sun’s warmth to make a serious contribution to household energy savings.

Modern PV systems run surprisingly well even under overcast skies and will continue to generate at least some electricity at quite low light levels – but as always, the sunnier the day, the better!

Many people installing solar systems also choose to invest in other renewable technologies to make up for times when the sun doesn’t shine; wind power or wood-burning stoves, for instance, can be used to make up the shortfall.

Is it Worth it?

That depends on how you view things. Neither system has a particularly fast pay-back, so unless you’re a householder planning to stay in your current home for a number of years, then looking at it from a purely economic standpoint, probably not; for community buildings the long-term answer has to be yes, for obvious reasons.

However, where this kind of approach really comes into its own is in terms of reducing your carbon footprint – a typical domestic PV installation saving around 1 tonne of CO2 emissions annually. According to World Energy Council figures, electricity from PV costs between 0.01 and 0.1 kg of CO2 per single kWh, five times lower than electricity from a gas-fired power station and at least 10 times lower than a coal-powered one.

Saving energy is not all about lower bills – though it’s certainly nice when it does!

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