SOLAR THERMAL
Solar thermal provides renewable hot water for the home by harnessing the sun’s energy. David Hilton explores the details
Solar thermal is a system using panels to create heat for use in domestic hot water. In the summer months, solar thermal panels could meet all or a substantial proportion of your domestic hot water demands. It is a simple, reliable technology which comes with a number of benefits.
Solar thermal isn’t a one-size-fits-all solution, and weighing up whether solar thermal panels are right for your home will depend on factors such as how much hot water you use, the orientation of your roof, and your existing fuel source.
There are two types of system: flat plate systems, which are cheaper to install, and evacuated tube systems, which are slightly more efficient. If the roof is close to due south then flat plate will be as good as evacuated tubes. Solar evacuated tubes can, however, be useful for difficult installations due to their higher efficiency — they can potentially be mounted on steeper pitches and on east- and west-facing roof pitches.
For the best use of solar thermal, a hot water store is required — meaning a system boiler configuration, which consists of a boiler and separate hot water cylinder.
HOW MUCH DOES IT COST?
A two- or three-panel solar thermal system will cost around £4,000 to £7,000 installed. This would supply an average 200 to 300 litre cylinder.
WHAT WILL THE SAVINGS BE?
Savings will depend on your hot water usage, the system design, and the fuel you are replacing (gas, electric, LPG, for instance).
For a four-bed house you would likely use around 200 litres of hot water per day, 365 days a year.
That would mean that you actually use around 12kwh of energy per day on hot water. If we assume that half your annual hot water comes from solar then this equates to 2,184kwh per year (12kwh x 182 days) of ‘free’ energy. Let’s compare that to the cost of producing the same energy using gas and electric: Gas: 2,184kwh per year x 7p* (average) = £152.88 Direct electricity: 2,184kwh per year x 28p* (average) = £611.52
A saving of £152.88 – £611 per year would give us a payback period of around 10 to 40 years on the capital cost of installing a solar thermal system, depending on use.
So, the real potential of solar thermal comes when you design it to give you more than 60% of your annual hot water and you make sure that the system is not oversized.
WIND TURBINES
Wind turbines convert the wind’s kinetic energy into mechanical energy. While less popular than other renewable options, a small 1kw-2kw wind turbine may still be a viable option for some homeowners. That solution might be improved by adding battery storage to the system, like the Sunamp or Tesla system.
Wind is a renewable energy source with no ongoing fuel costs but there are some considerations:
Wind speed and lack of turbulence are key. Generally the annual average wind speed needs to be over 5 metres per second (m/s).
The turbine needs to be sited away from buildings, trees and so on.
It must not cause ‘offence’ to neighbours (typically noise offence), listed buildings or national parks.
In some areas a bird or bat survey may be needed, or an environmental impact assessment. Check the requirements with the local authority and get prices before committing.
Wind turbines are complicated bits of kit with many mechanical components, which can fail. Look for those with comprehensive warranties.
INSTALLATION
Wind turbines will need planning permission. Neighbours may object, meaning the process can be expensive and timeconsuming. Your planning application will need to cover the likes of noise surveys, visual impact and ecological studies.
WHAT ARE THE COSTS?
A 5kw wind turbine would be usual for a domestic installation and will cost around £20,000-£25,000. After installation, with the work done to prep the site and get planning consent, the overall cost is likely to be around £30,000 to £40,000.
Smaller 1kw and 2kw turbines costs from £2,000-£4,000.
MICRO HYDRO TECHNOLOGY
Micro hydro technology is available that allows a homeowner (with a stream) to generate their own power. A hydro turbine of just 500W will produce enough electricity through the year to meet the annual consumption of an energy-efficient home. You could pick up and carry a turbine that size with one hand.
What’s more, pound for pound, it’s the most efficient of all the renewable technologies. A total life in excess of 40 or 50 years, with little annual cost, is not unreasonable.
You will need a stream or river nearby that is large enough, measured by ‘head’ – the vertical distance between the highest and lowest points of the stream and ‘flow’, which is the amount of water passing a point, measured in litres per second.
WHAT ARE THE COSTS?
Each scheme is specific to the stream and the price can vary hugely. According to CAT, the cost of a 1kw off-grid battery charging system ranges from £5,000 to £6,000. You may be able to pull together a micro hydro power set-up for under £10,000, but these costs may be up to £25,000.