Super efficient ground-air heat exchanger

What is described as a “super efficient” ground-air heat exchanger system has been launched by ADM Systems. It claims a Coefficient of Performance (COP) of around 50. This compares to a COP on ground-source heat pumps of around 3-4. It significantly reduces the amount of energy the mechanical ventilation with heat recovery unit (MVHR) system requires to heat or cool the incoming air.

It does this by exploiting the natural temperature of the ground to provide a cost effective source of renewable energy. At a depth of 1.5 to 2m, the earth’s temperature is a constant 8-12˚C throughout the year.

By drawing air through an underground network of pipes, it is either pre-heated by the ground in winter or pre-cooled in summer. In combination with an ADM Systems MVHR unit this significantly reduces the heating and cooling costs of a building.

For example, an outside air temperature of -5˚C during winter can be raised to +4˚C by the heat exchanger, before it enters the MVHR unit, based on a constant average ground temperature of 10˚C. Similarly, during summer a 28˚C outside air temperature can be pre-cooled to +16˚C, again by using the heat exchanger and constant 10˚C ground temperature, before it enters the MVHR unit.

Chris Marriott, ADM Systems’ managing director, says: “We’ve had a tremendous response to the new system from customers looking to significantly reduce their heating and cooling costs in the building. By using the earth’s natural stored energy we are able to offer an amazing COP of around 50.”

The MVHR units, fitted with the new system, works by a series of ducts that collect stale moist air from inside the house, from areas such as the kitchen, laundry and bathrooms. This stale contaminated air passes through the MVHR unit and is exhausted to the outside. Clean fresh heated (or cooled) air from the heat exchanger is then drawn into the MVHR unit, as the two air streams pass each other, the heat is transferred from the outgoing stale air to the fresh incoming air.

There is no mixing of air streams. During winter, the system is able to capture over 90% of the energy from the outgoing stale air before delivering it as warm filtered, preconditioned air into the living areas of the property through the ducting.

ADM Systems is able to offer customers bespoke design software to calculate the expected output of the system, based on UK weather data. This software shows the kilowatt-hours per annum that can be saved in both heating and cooling operations and also the COP of each project.

More information: www.admsystems.co.uk

Heat pump savings for care home

Residents of the newly built Potteries Court Extra Care Housing Scheme in Swinton, near Rotherham, are reaping the benefits of air-source heat pumps from Danfoss Heat Pumps, formerly ECO Heat Pumps.

The ground floor of the resource centre for the 11 bungalows and 24 apartments built by Chevin Housing Association has been fitted with an under-floor heating system, operated by two 10Kw air source heat pumps. This modern communal area is widely used by the elderly residents who live in the Potteries Court development as it houses a restaurant, lounge, meeting room, kitchen and washroom facilities.

The housing association was very keen to meet the Ecohomes standard and knew that heat pumps would increase its sustainability rating as well as reducing the carbon footprint of the development. As a result, Chevin Housing Association achieved a commendable ‘Very Good’ rating.

Heat pumps are becoming hugely popular for both new builds and refurbishments as they greatly reduce energy bills, compared with more traditional forms of heating. As a completely renewable energy source, they benefit from running costs that are typically 75% lower than conventional systems. This means they normally pay for themselves in five to seven years. Grants are also available for charities or public bodies through the low carbon buildings programme (LCBP).

Air source heat pumps are said to be rapidly increasing in popularity as they require no ground works. Potteries Court also makes use of rainwater harvesting techniques. The system collects surface water from the building’s roof and recycles it in order water the communal landscaped areas. Like the heat pumps, this also contributed to Eco-Homes rating points on this development.

Chris Boucher, project manager of Synergy Housing Solutions, part of the Chevin Housing Group, explains: “We were really keen to use renewable energy sources for the communal areas as all residents pay an annual service charge and fitting heat pumps helps to keep energy costs down. Not only that, but from our point of view as a housing association, they are a fantastic way of helping ensure that new developments achieve both our’s and the government’s regulations on sustainable housing.”

Air source heat pumps work by extracting low-grade heat from the outside air, similar to a refrigerator. However, where a fridge in the home expels heat from the inside to keep it cool, a heat pump will use it to provide heat for the home. The air handling unit draws air across the water-anti freeze solution and transfers this energy into the refrigerant. The refrigerant boils and the gases from this are compressed to produce temperatures in excess of 100_C. This energy is then used to heat the hot water, which is then circulated throughout the home.

Heat pumps are the most efficient method of heating a home because every 1kWh of electricity used to drive the heat pump generates around 4kWh of heat energy. This compares to the most efficient condensing boilers that generated 0.9kWh of heat for every 1kWh of electricity. This gives heat pumps a coefficient of performance of around 400 per cent compared to 75-90% for traditional heating systems

More information: www.ecoheatpumps.co.uk