Solar
layers of insulation in the roof, all of which improve the efficiency of the heat pump system. He did a great deal of research about the benefits of underfloor heating and how well this type of heat emitter works with a ground source heat pump. Charles put the underfloor heating in himself across the whole house, which was no mean feat as 3km of pipework was required for the ground floor alone as he designed the system to operate at 25°C to 30°C. He also did all of the internal plumbing which was a complex undertaking as there were multiple heat outputs including the ground source heat pump. He is currently devising a system which will automatically divert heat around the house as and when it is needed.
As he did most of the work himself, Charles made
use of Kensa’s MCS Umbrella scheme to make sure that the installation was properly accredited and therefore eligible for quarterly payments for the next seven years under the Government’s Domestic Renewable Heat Incentive (RHI) scheme. Since
installing the renewable heating system, the Lesters have received very small electricity bills for a property the size of Gwylfan-y-Glaerwen, and a generous sum in return through the RHI. Charles says: “If I was to offer advice to anyone thinking of installing a ground source heat pump, I would say don’t hesitate! It’s important to get advice from as many people as possible, but definitely talk to Kensa – they are experts and know what they’re doing. I would certainly recommend them.” Kensa's resident physicist and general manager, Dr Matthew Trewhella, provides his analysis of this interesting scheme: “This project is a great example of complementary design. Normally a property of this size would consume very large amounts of energy. Incorporating high insulation, passive solar design and active solar thermal has dramatically reduced the demand for heat. Providing heating and hot water using a ground source heat pump is always a good idea but the energy reduction improvements mean the efficient heat pump is only
used for heat that is absolutely necessary. “This not only reduces the running costs but also
decreases the initial investment – allowing Kensa to specify a smaller heat pump and smaller ground array. Even further improvements in efficiency are gained on this project by using excess solar thermal to recharge the ground array. In this case, this improves the system efficiency but in certain cases, it could be used to reduce the size and therefore capital cost of the ground array. “There are other ways to recharge the ground
array. As insulation levels increase, the demand for summer cooling is set to rise. A ground array can provide effectively free cooling whilst simultaneously recharging the ground array. Another exciting development is cooling of solar PV panels – solar PV operates more efficiently when it is cooler – by using a ground array to cool solar PV panels, we could improve ground source efficiency or decrease the size of the boreholes, lowering the capital costs.”
SOLAR SOLUTION SERVES NETWORK RAIL T
he installation of a 10-panel solar array featuring Stokvis Energy Systems solar collectors, to serve existing facilities at Birmingham International Rail Station, is being assessed as a potential pilot for a wider roll out of renewable energy across the facilities operated by Network Rail and Virgin Trains nationally. The project at Birmingham International – a station which serves both the NEC and the adjoining airport – was jointly commissioned by Network Rail and Virgin Trains, with renewables specialist ECO2SOLAR Ltd carrying out the installation of the Stokvis solar equipment. In addition to the 10 Stokvis DF100-6 Evacuated
Tube Collectors – offering a net absorber area 10.69m – the manufacturer also supplied a Stokvis Solar Bloc Maxi pump-station, and a Stokvis Resol BX Plus differential temperature controller, providing up to eight sensor inputs. Richard Davis, the engineer in charge of the
project for Virgin Trains, commented: "We chose to use Stokvis equipment because I was already aware of the company’s reputation for offering high quality products to the health sector and hotel chains; and have previously attended a seminar on their systems and products. This was always going to be a challenging retrofit, and although there have been some initial teething issues, Stokvis UK sales director, Keith Howard has been really proactive in resolving them. I believe we are going to see real savings." The solar fluid contained within the solar collectors is circulated by the solar bloc pump station to a large surface area coil contained within a 1,000 litre stainless steel thermal storage vessel. This provides a ‘pre-heat' for the domestic hot water, serving the station’s toilets and various shops and eateries around the main
A 10-panel solar array featuring Stokvis Energy Systems solar collectors installed at Birmingham International Rail Station
concourse linking to the airport and NEC. This solar preheat system raises the
temperature of the incoming mains water from a typical 10˚C to around 35˚C, although it is expected to reach a figure of 55˚C to 60˚C in high summer. The pre-heated cold water feed water then
serves two existing gas fired water heaters which then increase the DHWS to 60˚C. This arrangement results in the gas fired water
heaters not firing as regularly or having to raise the cold water supply from 10˚C to 60˚C as was previously the case.
The installation also features a heat meter to
measure the output from the panels in kilowatt hours to enable the client to assess not just the benefit of the system, but also the level of payment possible under the Renewable Heat Incentive (RHI).
www.heatingandventilating.net
May 2017
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