Stephen Andrews, Technical Manager at Danfoss Heat Pumps, looks at the reasons why increasing numbers of engineers are choosing to enhance their skills in the renewable sector.
When you consider the opportunities that the renewable sector offers over the next 10 years, it is little wonder that engineers are increasingly seeking to extend their skills to heat pump technology.
The coalition Government’s announcement that it intends to honour its commitment to renewable energy through the Renewable Heat Incentive, despite the public sector spending cuts, is great news for the renewable sector. Providing long term support for both ground and air source heat pumps, as part of a £850m investment, the Renewable Heat Incentive is expected to drive a tenfold increase in renewable heat over the coming decade. By doing this, the Government is determined to shift renewable heat into the mainstream, with the funding coming on stream in June 2011. The Government also recently stated that it believes renewable energy and the RHI is the way that Britain will achieve its carbon emission reduction targets.
Heat production is responsible for around half of the final energy demand of the UK and half of UK carbon emissions. The aim through schemes like the Renewable Heat Incentive is that by 2020 we will have moved from 1% of heat energy produced by renewables to 12%. And it looks like this will be open to many different sectors, including businesses, schools and domestic installations.
The key to designing a heat pump system is to keep it simple. We find that most problems with heat pump configurations come about because of an over complicated layout. Part of the training we offer specifically for the commercial sector involves a module on system design and this is an area where we provide support for engineers, especially in the early stages of working with heat pump technology.
As with all good heating arrangements, we recommend that wherever necessary, heat pumps are cascaded and therefore there is no over-reliance on any single system. With a master and slave arrangement, heat pumps (ranging from 20-42 kilowatts) can be sized to meet the requirements of the project.
The great thing about this arrangement is that if any problems arise, for example, the master stops working, the other heat pumps are unaffected and the system can continue, with another heat pump reconfigured as the master. Problems are rare with our heat pump systems if the installation procedure is followed correctly.
The majority of problems are caused at installation stage and this normally involves air, dirt or incorrect brine mixture in the system, which leads to either noticeably high or low pressure from the heat pump. Our training covers installation in some depth, including how to troubleshoot any issues, such as avoiding extremely high or low pressures. To remedy this, we demonstrate how the system can be purged and the filters cleaned out and replaced relatively easily.
We recommend a simple, bi-annual service of a heat pump system, which is normally done by the service engineer or facilities manager on site. Obviously, servicing should be carried out prior to the heating season (September) and at the end of the heating season (normally June), as part of maintaining optimum efficiency and preventing problems. This should involve monitoring the heat pump cycle and making sure the settings are checked to ensure the flow of brine is OK.
Some projects require automatic monitoring of the performance of the heat pump and again this could be done by service engineers. It is possible to access data relating to the heat pump efficiency, in order to analyse what performance it is achieving and this is also a good opportunity for the engineer to spot any preventative maintenance work that may be required before it becomes an issue. The systems can also be monitored remotely via an internet link.
There is still a misconception that heat pumps cannot provide both space heating and hot water in large installations. However, a typical heat pump can deliver water temperatures of 50°C and if higher temperatures are required for specific industries, then this can be boosted by use of a de-superheater in the refrigerant circuit, which is standard in all Danfoss light commercial heat pumps.
For engineers and installers, heat pumps represent a lucrative income stream, as the average per job value can be significantly higher than for a conventional boiler. However, with a heat pump, it is a completely different approach to installing a gas boiler or other heating system. As it is not reliant on a combustible fuel, but rather a slower, more natural technology, it is important to plan a long term strategy for the heat pump over the year. This includes studying the requirements for heating and hot water at certain times of the year and working out what the base load requirements will be.
The use of heat pumps is rapidly increasing in the commercial sector, especially where there is no mains gas supply. All heating systems, including heat pumps, work best when insulation is good, when there are no draughts within a building and where the doors are not left open for long periods making them unsuitable for a warehouse or factory setting. A good heat distribution network is also essential – and this is why underfloor heating systems are so widely specified with heat pumps.
Weather compensation systems are one of the major advantages of our heat pumps. Instead of being governed by heat sources through zone-controlled thermostats cycling on and off throughout the day, heat pumps are constantly on, selecting their temperature determined by conditions outside the building. This ensures a more comfortable environment for building occupants and more consistent temperatures, rather than experiencing the high and low temperatures of traditional boilers.
Good practice within a maintenance schedule is to check the refrigerant level of a heat pump at least once a year, and again we cover these types of essentials on our courses. With our systems, the refrigeration units are hermetically sealed, which means the risk of any leakage is minimal. The weight of our refrigerant is also below the limit that is legislated by F Gas legislation, which means they are not subject to annual assessment by an external body every year.
With commercial building owners constantly looking for ways to reduce their carbon emissions and energy costs, the switch to renewable technologies offers a major opportunity. The rising price of gas has also combined with the Renewable Heat Incentive coming on stream, meaning that the landscape for energy in commercial buildings is changing rapidly.
Increasingly often, there is a requirement to link heat pumps with existing boilers or to integrate other renewable technologies, such as Solar PVs. In the case of Solar PVs and large wind turbines, these can work particularly well in offsetting the electrical energy used to power the heat pump, leading to a carbon neutral installation.
With the support out there for engineers and facilities managers, in terms of training, design and technical support, there is a great opportunity for commercial buildings to reap the benefits of this cleaner, greener source of energy.