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What are Heat Pumps ?

Heat pumps are devices that generate their heat by utilizing the heat that is contained within the ground and air all around us. A heat pump has the ability to extract heat from one environment and discharge it into another and do the same with cooling. Heat pumps contains three parts, the energy collector which would be located in the medium to absorb the heat, the fridge compressor itself and the distribution system.

Why Use Heat Pumps?

 A heat pump is one of the most effective ways to heat or cool a building using renewable energy. Unlike many other forms of renewable energy that depend on the sun shining or the wind blowing, the energy for the heat pump is always available. Heat is widely available in the ground, air and water around your house. These natural sources of heat are constantly replenished by the sun, wind and rain. A Heat Pump system will harness these free and renewable energy sources for heating your house and supplying hot water at a very low cost. Heat Pumps are very economical, for every kW of electricity used to power the Heat Pump, 3 to 6 kW of heat is generated.

Benefits of using Heat pumps

  • Unlimited heat available from ground and air
  • Economical – provides operating cost savings of 30% to 60%?
  • Comfortable – maintains an even temperature and humidity level throughout  your home.
  • Safe – no open flames, no fumes, no soot and no carbon monoxide.
  • Flexible – one single unit handles heating, cooling and hot water.
  • Dependable – contains few moving parts and requires little or no maintenance.
  • Value – increase the value of your home along with decreasing your heating and cooling bill.
  • Efficiency – as much as four times as efficient as conventional systems.
  • Low running costs – e.g. heat 2,500 sq ft house for as little as €400 per year.
  • Environmentally friendly – our systems emit no carbon dioxide, carbon monoxide or other greenhouse gases.
  • Units available for all sizes of dwellings – new and existing.
  • Improve Building Energy Rating (BER).

How Heat Pumps Work?

Heat Pumps work on the same characteristics as a standard domestic fridge but in reverse, instead of cooling, it heats. Heating and cooling are achieved by moving a refrigerant through various indoor and outdoor coils and components. A compressor, condenser, expansion valve and evaporator are used to change the state of refrigerant from a liquid to hot gas and from a gas to cold liquid.

Main Stages

  1. The refrigerant (liquid state) passes through the outdoor evaporator coils at a low temperature.
  2. The water/antifreeze from the ground loop enters the unit and heat is transferred from this water/antifreeze to the refrigerant. The refrigerant begins to boil and changes to a vapour.
  3. The vapour is pressurized by the compressor where the temperature is increased to over 100 degrees.
  4. The vapour then enters the condenser heat exchanger and the heat is given up to the coils. At this point, the heat is transferred to the buildings heating, and hot water systems. As it passes through the coils, it cools and turns back into a liquid.
  5. The refrigerant which is now cooled liquid at high pressure passes through an expansion valve, which reduces the pressure so that the liquid can re-enter the evaporator and begin the cycle again.

More on the Efficiency of Heat Pumps

Heat pump efficiency (COP) is obtained by comparing how much energy it consumes in order to complete the heating and cooling cycle. Coefficient of performance (COP) defined as: “The ratio of heat delivered by the heat pump and the electricity supplied to the compressor”

(COP = Kilowatts Delivered) eg. 7.5kw (Output) ÷ 1.5kw (Electrical Input) = 5 COP

Electricity is needed to drive the heat pump, but for every unit of electricity used, it will generate 3 to 5 units of useful heat. The efficiency of a heat pump will depend mainly on the temperature of its energy source and the temperature at which the heat generated is needed. Basically, the higher the temperature of the heat source is and the lower the temperature of the useful heat is, the more efficient the heat pump will be. A Ground Source heat pump using the soil as a heat source (constant temp of 8°C to 12°C) and floor or wall heating (water temp of 35°C to 55°C) is one of the best combinations, with an efficiency in excess of 450%, compared to an oil or gas boiler with an efficiency of 70 – 85%.

What is a Good Source of Heat?

A heat source is any area, object or mechanism that contains heat. We offer the full range of collectors and will design the system that best suits depending on the available land or water source, the local geology and the heating requirements. The different types of collector available are described below.

 

Closed Horizontal loop

Horizontal loops are often considered when adequate land surface is available. Pipes are placed in trenches in lengths that range from 30m to 120m.

 

 

 

Vertical loop

Vertical loops are the ideal choice when available land surface is limited. Drilling equipment is used to bore small – diameter holes from depths of 60m to 120m (200 to 400 feet) deep. Special U bend fittings are used at the bottom of the bore hole to connect the pipes.

 

 

 

Pond (lake)

Pond (lake) loops are very economical to install when a body of water is available, because excavation costs are virtually eliminated. Coils of pipe are simply placed on the bottom of the pond or lake.

 

 

 

Open loop system

Open loop systems utilize ground water as a direct energy source. In ideal conditions, an open loop application can be the most economical type of geothermal system. Although predominantly used for commercial applications these can be economically utilized for domestic use where the water table is high.

 

 

Air Source

The heat pump is placed outside the building and extracts heat from the outside air using sophisticated heat exchangers; this heat is then transferred into your home.

 

 

 

Is Air Source Better Than Ground Source?

Of late, Air Source Heat Pumps (ASHP) are attracting more attention than Ground Source Heat Pumps (GSHP). However, from our experience, we have found that GSHP’s give better better running costs, higher efficiency’s, lower maintenance and longer life. ASHP’s efficiency’s and running costs are within 15% of GSHP. However ASHP’s are up to 30% cheaper to install, therfore it would make financial sense to have installed on smaller dwellings. Therefore we are likely to see a swing back towards GSHP popularity in the coming years.

What Is a BER?

A Building Energy Rating (BER) Certificate calculates the energy performance of a building on a scale from A-G. A-rated houses are the most efficient and G the least efficient. All new dwellings and houses offered for sale or lease require a BER.

There are two types of BER, a provisional and final BER. A provisional BER is based upon plan and specifications of a new building and is valid for 2 years. A final BER is issued on completion of a new building and is valid for 10 years once there is no material change to that building. Existing buildings may also have a BER assessment carried to to determine their efficiency and that certificate is also valid for 1o years.

The BER is calculated by assessing the major components of all the building in detail. The U-values of walls, roofs, floors, windows and doors and calculated as well as the efficiency of the heating system and hot water system. Mechanical ventilation, air tightness, energy efficient lighting and renewable technologies are all assessed and combined to give the energy rating of that building.

Once the BER is calculated there is a large amount of information available such as annual energy use for space heating, water heating, ventilation, lighting and associated pumps and fans.

 
The building Energy Rating (BER) is an indication of the energy performance of this dwelling. It covers energy use for space heating, water heating, ventilation and lighting, calculated on the basis of standard occupancy. It is expressed as primary energy use per unit floor area per year (kWh/m2/yr).

What Is a U-Value?

If you are thinking of building a house, understanding the concept of U-Values is very important. A U-Value is a measure of heat loss in a building element such as a wall, floor or roof. It can also be referred to as an ‘overall heat transfer co-efficient’ and measures how well parts of a building transfer heat. This means that the higher the U-Value the worse the thermal performance of the building envelope. A low U-Value usually indicates high levels of insulation.
Useful Summary of the minimum U-Values Required;
Ideal U-Values Of A Domestic Dwelling
However, merely meeting these standards may not be enough to comply with the building regulations. If the building is poorly oriented or has a large proportion of glazing, this may require a further improvement and compensation in terms of U values, airtightness and thermal bridging so as to meet the overall energy requirements. See Building Regulations 2011, Part L for more information.

What is Part L of the Building Regulations?

Part L of the Building Regulations refers to the conservation of fuel and energy. It states that ‘a building shall be designed and constructed so as to ensure that the energy performance of the building is such to limit the amount of energy required for the operation of the building and the amount of carbon dioxide emissions associated with this energy use insofar as is reasonably practible’. 
For Existing Buildings, the requirements shall be met by;
(a) limiting heat loss and, where appropriate, maximizing heat gain through the fabric of the building;
(b) controlling, as appropriate, the output of the space heating and hot water systems;
(c) limiting the heat loss from pipes, ducts and vessels used for the transport or storage of heated water or air;
(d) providing that all oil and gas fired boilers installed as replacements in existing dwellings shall meet a minimum seasonal efficiency of 90% where practicable.
For New Buildings, the requirements shall be met by;
(a) providing that the energy performance of the dwelling is such as to limit the calculated primary energy consumption and related carbon dioxide (CO2) emissions insofar as is reasonably practicable, when both energy consumption and carbon dioxide (CO2) emissions are calculated using the Dwelling Energy Assessment Procedure (DEAP) published by Sustainable Energy Authority of Ireland;
(b) providing that, for new dwellings, a reasonable proportion of the energy consumption to meet the energy performance of a dwelling is provided by renewable energy sources;
(c) limiting heat loss and, where appropriate, availing of heat gain through the fabric of the building;
(d) providing and commissioning energy efficient space and water heating systems with efficient heat sources and effective controls;
(e) providing that all oil and gas fired boilers shall meet a minimum seasonal efficiency of 90%;
(f) providing to the dwelling owner sufficient information about the building, the fixed building services and their maintenance requirements so that the building can be operated in such a manner as to use no more fuel and energy than is reasonable.
Link: Building Regulations, Part L (2011)

Triple Glazed Or Double Glazed?

Triple glazed windows are typically more energy efficient than double glazed windows and can achieve a U-Value as low as 0.6W/m2K versus a U-Value for a high standard double glazed window of 1.2W/m2K. However, triple-glazed windows are typically considerably more expensive than double-glazed windows. For this reason, investing in triple glazed windows is more suited to a situation where there is a high level of insulation,with a very good BER, i.e. an A-rating. This is because if a house has a lower level of insulation, the investment in triple glazed windows with a low U-value would not be cost effective as heat retained would be lost through the other fabric elements of the house such as through the walls.
The Following is a Comparison of Various Glazing Types;

 

What is HRV?

Heat Recovery Ventilation (HRV) is an energy recovery ventilation system that uses sophisticated heat and air exchangers between the inbound and outbound air flow. HRV systems provide fresh air and improved climate control, while saving energy by reducing heading demands. There would be no benefit to install a HRV system in an old house with natural (draughty) ventilation. These systems only work effectively in houses that are adequately air tight and insulated.
What Is Air-Tightness?
Air-tightness is the control of air flow through the external envelope of a building. If a building is air-tight, air will not leak from the structure via common paths such as:
  • Ceiling and Wall Junctions
  • Plaster Board Joints
  • Doors
  • Windows
  • Service Entry Points
  • Etc.
Any leaks would create discomfort and heat would be lost, which would result in the heating system having to compensate for heat loss.

Why Use a kWh Meter?

Unlike conventional heating methods such as oil or gas, heat pumps prove tricky to work out exactly how much it costs to run. This is due to the Heat Pump sharing its electricity bill with other electrical appliances around your home. Therefore with each of our heat pump installations, we include a kWh meter in order to calculate the energy usage of the Heat pump.