2. Solar Thermal Systems for hot water
Solar Thermal Systems use the sun’s warmth to heat water, which is stored in a twin coil hot water cylinder. There are two types to choose from: flat plate, which is cheaper, or evacuated tube, which is more efficient. The Energy Saving Trust recommends installing about one square metre panel per person and a well-specified system delivers around 60% of a family’s annual hot water requirement – reducing energy bills and lowering your carbon footprint. You’ll need a boiler or heat pump for heating and to provide hot water when the system isn’t producing enough during winter months.
Solar water heating qualifies for the Renewable Heat Incentive (RHI), a government scheme that pays householders for generating heat using renewable energy. Properties need to meet minimum efficiency standards and the current rate is 20.06p per kWh.
‘While solar thermal isn’t as popular in the UK as it was, and it often loses the battle for roof space with solar PV, the technology is well subsidised by the RHI. We’d strongly advise anyone installing a heating system to make it solar thermal compatible, if not for now, then for the future,’ says Darren McMahon, marketing director at Viessmann.
3. Integrated solar panels for listed buildings or conservation areas
New technology is bringing integrated panels and tiles to self-builders and renovators who want to incorporate solar PV or ST systems into the fabric of their roof.
‘Integrated solar panels are fixed above roofing membrane and battens, replacing the tiles for a sleek, low profile,’ says Stuart Elmes of Viridian Solar. Solar slate roof tiles are unobtrusive, improve energy efficiency and are an option for listed buildings and conservation areas.
The experts at Viridian Solar also explain the benefits of opting for above-roof solar PV over roof-integrated solar PV. ‘Above-roof systems will operate at a lower temperature due to better ventilation. Since soar PV power output falls as panel temperature rises the argument goes that roof integrated solar will have a lower energy yield.
Viridian Solar and researchers from the University of Cambridge have examined this effect. The published research found that the reduction in energy yield was very small, of order only 3%.’
Photo: Flat-plat ST system with ThermoProtect, from £4,000, Viessmann
4. Evacuated tube solar thermal systems for efficiency
A solar array doesn’t need to be mounted on the roof but it does need to be as south-facing as possible, and set on an incline close to 30 degrees, otherwise performance drops off. Evacuated tube solar thermal systems are slightly more tolerant to being other than south-facing, but to work effectively all panels need to be free from any shadows cast by surrounding trees and buildings, plus PV panels need more roof space.
The UK’s premier energy saving advice portal, The Green Age, describes how ‘solar thermal harness the sun’s energy by turning the solar radiation into heat which is usually used for water.’
They go on to advise that a ‘typical evacuated tube solar collector system will cost about £3,000 – £5,000 to get installed on your property, and will typically produce about 1,000 – 2,500 kWh of useful heat – or about 50% of your hot water requirements. As long as you get it installed by a MCS approved installer you will then be entitled to the renewable heat premium payment grant which for solar thermal installations is about £600.’
Photo: Greenonetec ST system with panels around 4sqm, from £4,000, Norfolk Solar
5. Photovoltalic Thermal Systems for renewable low-cost energy
A photovoltaic Thermal System (PVT) yields hot water and electricity from the same panel. Systems don’t benefit from the FIT or RHI incentive schemes, so PVT is for people who want to reduce running costs by producing as much renewable low-cost energy as they can.
New innovations allow hybrid panels to use wasted heat from electricity generation and convert it to energy for hot water.
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