Green technologies at Merlin Farm
Ground Source Heat Pump
A Ground source heat pump is used to heat the 3 Eco Cottages at Merlin Farm.
The heat pump system harnesses natural heat from underground by pumping water through it. The heat pump then increases the temperature, and the heat is used to provide home heating. The pump needs electricity to run, but the idea is that it uses less electrical energy than the heat it produces. The heat pump performs the same role as a boiler does in a central heating system, but it uses ambient heat from the ground rather than burning fuel to generate heat. Unlike an air source heat pump, which takes heat from the air.
Ground source heat pump systems are made up of a ground loop (a network of water pipes buried underground) and a heat pump at ground level. A mixture of water and anti-freeze is pumped around the ground loop and absorbs the naturally occurring heat stored in the ground. The pump itself consists of an evaporator, a compressor and a condenser - together these take the heat from the water mixture, transfers it to the heating system and increases the temperature in the process. A ground source heat pump increases the temperature from the ground by between one and a half and four times – so if the ground temperature is 12°C, the output would be between 18 and 48°C). This heat is then used in the underfloor heating system. The ground source heat pump system helps to lower our carbon footprint as it uses a renewable, natural source of heat – the ground. According to the EST, a heat pump with mid-range efficiency uses a third of the energy needed in an average gas or oil boiler to produce the same amount of heat. A heat pump also requires electricity to power the heat pump, so there would still usually be some resulting CO2 emissions, but at Merlin Farm we generate our own electricity too!.
Solar Water Heating
Solar water heating systems, or 'solar thermal' systems, uses free heat from the sun to warm the hot water in our Cottages. An immersion heater assists to provide hot water when solar energy is unavailable. Solar panels called collectors, made up of evacuated tubes are fitted to the lean to roof in the car park The tubes absorb incoming solar heat energy and the casing minimises heat loss. A fluid is circulated through the tubing and this fluid heats up as it passes through the absorber plate. The immersion heater is used as a back-up to heat the water further to reach temperature. Solar is one of the most established of all the renewable energy technologies and provides roughly half of our hot water requirements across the year. During the summer months they contribute towards nearly all of our hot water needs. During the winter months we may need to top up the system with the help of the immersion heater.
Merlin Farm generates it's own electricity onsite via 216 Solar Photovoltaic (PV) panels installed in our bottom field. Solar PV systems use cells to convert sunlight into electricity. The PV cell consists of layers of a semi conducting material. When light shines on the cell it creates an electric field across the layers causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity. The Solar Cell is the basic building block of Solar PV technology. Most people are familiar with PV Solar Cells that power calculators. These cells are wired together to form a module (PV Solar Panel). The PV Modules gather solar energy in the form of sunlight and convert it into direct current (DC) electricity. An inverter can convert this DC power into alternating current (AC power). PV cells are referred to in terms of the amount of energy they generate in full sunlight; known as kilowatt peak or kWp. On a sunny day our solar panels generate enough electricity to power the Eco Cottages and any surplus energy is exported back to the grid.
Energy Efficiency Rating of our Eco Cottages
Large double glazed windows and doors filled with argon gas and the levels of insulation used has assisted in us gaining an excellent energy efficiency rating.