Heatpumps
For climates like Ireland, with moderate heating and cooling needs, heat pumps can offer an energy-efficient alternative to furnaces and air conditioners. Like your refrigerator, heat pumps use electricity to move heat from a relatively warm space to a cooler space.Heat-pumps take heat some heat from the ground and use electricity to pump this warmed water through a circuit for water and space-heating. There are several types of heatpumps. They are rated in order of efficiency below;
- Vertical Borehole (water) heat-pump
- Shallow lake (water) heat-pump
- Horizontal (groundsource) heat-pump
- Air-source heat pump
On average, the first two will deliver approximately 5kW of heat energy for every 1kW of electricity. A ground source heatpump will deliver about 4kW of heat for every 1kW of electricity. While an airsource heatpump will provide 3kW for every 1kW. This obviously has a bearing on the payback time for the investment. The capital cost of the equipment should be weighed up against the savings being made on space heating.
In order to calculate your savings, you should find out what your house or a house similar in size to yours, uses each year in heating energy costs. In a recent document the Irish government’s renewable body SEI provide the example of a 120m² house using 27,456 kWh of energy per annum for space heating, costing €985 per annum on heating oil. If heating oil costs 60c per litre, this equates to 1597 litres of oil per annum.
With a heat pump, you would pay for ¼ of this 27,456kWh of this heat energy. This means you would pay for 6864kWh of electricity. Night saver rate is 7.05c per kWh while day rate is 14.35c per kWh. It is therefore very important that night saver rate is chosen by somebody using a heatpump. On night rates the heatpump for this house would cost €48 euro per annum, at present rates.
So, to use the SEI’s 120m² example, you would save €985 per annum on space heating. The minimum time it will take to pay back this cost is the cost of installation divided by the savings.
A
heat pump is technically very similar to a refrigerator in the way it
operates except that a heat pump is usually used for heating rather
than cooling. In other words, when used for heating, a heat pump
operates like a refrigerator in reverse.
In
a domestic fridge, heat is “pumped” from an evaporator inside
the refrigerated compartment to a condenser (see photo on right) on the back of the
refrigerator. Thus lowering the temperature of the refrigerator and
warming the kitchen. The condenser on the back of a fridge is a
familiar shape to many people, consisting of an “S” shaped pipe
with a grill.
In
a heat pump, the evaporator is located somewhere in the external
environment or outdoors. Heat is then pumped from the outdoor source
to a condensor inside the building which is warmed as a result. The
condensor then gives its heat to the heating system in the house. As
a result of taking the heat from the outdoor environment, the area
around the evaporator can be cooled by an appreciable degree.
The heat pump process is made possible by a special refrigerant liquid that boils at low temperature.
Ground source heat pumps are sometimes called “geothermal”. In an Irish context, there is little geothermal activity of significance when compared to countries like Italy or Iceland. Geothermal activity in Ireland is hinted at by the locations of traditional spa towns. In these locations, water was traditionally heated up to warmer temperatures than other areas and used in tourist spas. Examples in Ireland include Lucan and Mallow. Closer to these areas geothermal heat pumps probably make more sense than in other areas.The perfect geothermal source would have the following three factors;
An aquifer containing water that can be accessed by drilling
An impermeable cap rock (e.g clays or shales)
A Heat source (e.g crystillasing granite)
The soil type is an important consideration that should be considered by the professional installing your heat-pump. In Ireland, a free draining soil type works better for heat pumps.
Please feel free to contact BEO if you have a query relating to heat-pumps in Ireland.