As a nation, we have been pretty slow on the whole heat pump technology. What better way to provide heating and hot water to your home or business than to extract it from the air, ground or even a nearby lake or stream.
How does a Heat pump work?A heat pump heating system consists of three components; a heat source, a heat pump and a distribution system. Heat pumps use a small amount of electricity to convert heat energy by using a refrigeration cycle to absorb heat from the heat source and raise it to a useful temperature for heating and hot water requirements.
The process a heat pump uses is a very simple one;
- Energy is taken from the heat source, be that air, ground or water.
- Your fuel, electricity, is used to drive the heat pump, powering either a fan or pump to collect this energy.
- The collected heat energy is transferred to the refrigerant inside the heat pump’s evaporator which in turn causes the refrigerant’s temperature to rise, changing its state from liquid to gas.
- The refrigerant gas is then compressed using an electric compressor. This compression reduces its volume and increases its temperature.
- A condenser (or heat exchanger) then extracts the heat energy from the now hot compressed refrigerant gas, transferring it to the water within the central heating circuit, and allowing the refrigerant to return to its liquid state again; ready to repeat the process all over.
The more efficient the heat pump, the less electrical energy is used over the year to extract the same amount of heat. This efficiency is detailed by the Co-Efficient Of Performance (COP) or Seasonal Co-Efficient Of Performance (SCOP) of the unit. The higher this number, the better for both running costs as well as having an impact of your RHI tariff.
A normal rule of thumb is that air source heat pumps are have a designed SCOP around 3.0 with water and ground source heat pumps around 4.0. The most efficient solution possible is achieved by combining a high efficiency ground source heat pump with a solar thermal collector linked into the ground loop, effectively pre heating the collector. Here at Energyzone we have examples of this technology in the field with COPs approaching 7.0.
The reason for this difference is the variance in temperature of the source the heat is being drawn from; for an air source the outside air temperatures fluctuate and tend to be at their lowest when you require the most heat from your heat pump. For a ground source when sized correctly, the ground will remain at a more constant temperature, thus yielding more heat for less effort, or in this case, less electricity.
How is heat stored?Heat energy for your showers and taps etc. is stored within a cylinder, an unvented fully pressurized model if your water pressure is sufficient, containing an oversized heat pump rated coil. This allows for plenty of surface area from which heat from the heat pump is transferred into the water stored within. This water can then be used to supply all of your hot water services.
How is heat distributed through the building?The heat collected can be distributed just like any other heating solution with the use of radiators, underfloor heating or via warm air ducting as part of a ventilation solution or a combination of all three. Unlike conventional heating systems, it is important to realise that heat pumps differ to gas and oil boilers because they deliver heat at lower temperatures over much longer periods. During the winter they may need to be on constantly to heat your home efficiently. You will also notice that radiators won't feel as hot to the touch as they might do when you are using a gas or oil boiler but when sized correctly, will comfortably heat the space to designed levels.
Air, Water, Ground or Solar Assisted?Heat pumps can be effectively broken down into three types, and this is reflected on the medium they use to draw the heat from; air, water and ground with the latter able to utilise a solar thermal supply, a pre heat if you will. Air source heat pumps are usually easier to install than ground source as they don't need any trenches or drilling, but they are less efficient than ground source heat pumps. The additional cost and space required for a ground source is a greater than the installation cost of the air source units, but the long term running costs are less and currently the Renewable heat incentive payments from the Government are 2.5 times more. Water source heat pumps can be used to provide heating in homes near to rivers, streams and lakes, essentially these are ground source units minus the buried pipework but, just like an appropriately sized ground collector, the water source needs to be of sufficient volume and temperature.
When designed correctly, a heat pump can be engineered to completely replace your existing Oil or LPG Gas boiler, saving at least a third on your current fuel bills. At the same time, heat pumps qualify for the Government backed incentive; the Renewable Heat Incentive or RHI.
Renewable Heat IncentiveOn a Domestic level, this payment is based upon the deemed space and water heating figure calculated for your home culminating in four quarterly payments every year for seven years regardless upon your actual systems usage.
On a Commercial level this payment is a measured one, meaning payments are based upon actual heat generation. The tariff duration is 20-years with systems being designed to provide heating and hot water to, in many cases, more than one property.
Here at EnergyZone we pride ourselves on being at the top of the game when it comes to engineering innovation, this is no more apparent than with our range of heat pump solutions. Alongside the standardised installation options, we are also able to offer several add-ons, all designed to improve outputs and maximise system running costs.