Making the most of LPG
With buildings being responsible for nearly half the UK’s energy consumption and carbon emissions, building services managers are under pressure to improve the energy efficiency of the buildings they are responsible for. This is the case in both urban and rural areas, for all types of commercial buildings – ranging from offices, factories and processing plants to leisure facilities, hospitals and schools.
And with climate change continuing to be one of the Government’s top priorities and energy costs increasing in line with spiralling oil prices, things are very unlikely to change.
Therefore, in recent years, renewable technologies, which use the earth’s free and natural resources to create energy, have been developed by the UK’s leading heating manufacturers. These heating technologies have elements that are zero carbon or carbon neutral, and the systems as a whole produce very few greenhouse gas emissions.
Heat pumps are one of the renewable heating products available today. Heat pumps extract thermal energy from a variety of renewable sources, including the air, earth or water, and upgrade it to a higher, more useful temperature. A heat pump absorbs heat where it is plentiful, then transports it and releases it in another location, where it can be used for space and/or water heating. Heat pumps work on the same principle as a domestic refrigerator, but in reverse.
Ground and air source are the most widely available types of heat pump. They both produce less carbon emissions than conventional heating systems, and are very energy efficient – for each kilowatt of electricity used to run the heat pump, three to four kilowatts of heat are delivered. Usually, an ample supply of electricity and good insulation will be required for heat pumps to work effectively, and for them to reach these levels of efficiency.
Ground source heat pumps utilise the earth’s natural solar energy, but obtain heat absorbed by the ground, rather than from the sun as a solar thermal water heating system would. The sun’s rays can reach below ground, and the earth’s crust acts like a battery, storing the heat. So, as a result, just two metres below ground the earth is constantly warm, being around 12oC.
This heat can be pumped out of the ground and transferred via pipework, and can then be used for space and water heating. The pipework is either laid quite shallowly across the earth in ‘S’ bends (known as ‘slinky coils’), is laid in horizontal trenches or is bored deep into the ground.
Air source heat pump technology is very similar to ground source, but here heat is extracted from the surrounding air rather than the ground. It is possible to extract considerable heat from the air, even at temperatures as low as minus 15°C. The heat is passed via a heat exchanger into water and is used to provide space heating, but it can also be used for water heating and, in some cases, cooling.
It should be noted that air source heat pumps are less efficient than ground source heat pumps; air loses heat more rapidly than the ground does and more pumping (and therefore electricity) will be required. Air source heat pumps are very dependant on the ambient air temperature, so this could be an issue in colder months when there might not be any heat to extract – and of course the available heat will vary quite significantly throughout the year. However, there is a benefit in the fact that air source heat pumps need less space than ground source varieties.
With both ground and air source heat pumps the heat is relatively low-grade, so is typically released into a property through an underfloor heating system. Therefore the most ideal time to install them is when a building is being constructed or extended, or during a refurbishment programme.
These heat pumps can also be used for water heating, but, when trying to raise the temperature of water above 35oC, they become much less efficient. There is also a risk of legionella if a high water temperature (we suggest at least 65oC) is not achieved.
It is therefore standard practice to put in an additional water heating system for sanitary water – and this is why non-mains-gas fuels still play an important role when this type of renewable technology is being specified.
Having the lowest carbon emissions out of all the fossil fuels available in non-mains-gas areas (and emitting 19% less CO2 per kWh than heating oil), LPG is a very effective complementary fuel source for heat pump systems (as well as other new technologies like solar thermal water heating and CHP). If a commercial or public sector property also prepares hot food, which is likely to be the case in hotels, schools and universities, prisons and hospitals, LPG can be used to fuel the cookers too.
One example of a ground source heat pump and an LPG boiler working together successfully is at a new healthcare centre in North Wales. Here the two technologies provide sufficient heating and hot water for the building, and the property owner is already benefiting from reduced fuel bills.
There is now another type of heat pump for building services managers working in non-mains-gas areas to consider; an innovative and energy efficient LPG-powered product. Being marketed by Calor and distributor Oceanair, the Sanyo gas heat pump provides heating and cooling for non-mains-gas commercial applications with a limited electricity supply. The product can also be used in inner-city areas, in applications where there is a lack of three-phase power and inadequacies in the mains gas supply.
Sanyo’s gas heat pump is a Variable Refrigerant Flow air conditioning system, comprising an internal combustion engine which drives a refrigeration compressor and then produces heating and/or cooling. The gas heat pump delivers environmentally friendly heat, and ‘free’ hot water if required, while providing energy efficient, innovative air conditioning and reducing electrical demand. The product is over 100% efficient; achieving 140% efficiency in heating and 160% efficiency in cooling. The efficiency can be even higher than this if either hot water for sanitation or perhaps a leisure facility is heated by the gas heat pump’s gas engine during the cooling cycle, or if Sanyo’s 4kW electricity generation unit is added to the heat pump.
Though the gas heat pump can be used in a wide range of commercial buildings, including offices and factories, it offers significant benefits for hotels, holiday parks, leisure centres and golf clubs where mains gas is not available or practical.
There are now many solutions available for businesses looking to save energy and reduce carbon emissions, with heat pumps being just one of the options. But building services managers don’t have to opt for just one type of technology – in areas where mains gas isn’t available, renewable energy can be successfully mixed with non-mains-gas fuels, and in some cases doing this can help to achieve the desired outcome, for example if the domestic hot water isn’t reaching an adequate temperature through using renewable energy alone. We therefore believe that non-mains-gas fuels will continue to play an important role in the heating solutions of the future.