The design of your system really is the most important phase of the project. If this
is not completed correctly, the system will never perform at an optimum level.
One glove certainly does not fit all, especially with renewable energy systems. Toomany times, we have been called to completed projects, which simply are notworking. The vast majority of the time this can be traced back to a poorly designed system, which was never going to provide the client with what they required.
Most manufacturers will provide a very basic design for a system, which would gettheir product working. However, this design will not provide you with the efficiencythat is needed to get the most out of a renewable energy heating system. We willensure that this basic de-sign is expanded on, to get the most out of the technology and get it working in harmony with the rest of the system.
As the energy extraction is from the ground, it is important that the proposed areais suitable for to meet the requirements and support the heat load.
Thermo Geological Engineer Consultants will normally be commissioned for thedesign of Borehole and ground loop arrays. This determines the exact extractionrate from the ground, the make up and also the flow requirements through the ground array.
If the correct procedure is not followed then a possibility of over extraction islikely. This will cause devastating system failure and potentially carry the huge costs of reinstatement.
Heat pumps generically deliver energy to the heating systems at much lower flow
tempera-tures. This clearly apparent with the radiators not being too hot to touch.
The heat energy flow temperature to the heating system from a heat pump will onaverage be 40/45C at -5C external temperature. On highly insulated houses even lower.
In complete comparison, an unrefined designed heating system, working with agas/oil boiler will deliver flow temperatures of 75/80C. Due to the high flowtemperatures it allows most poorly designed heating systems to operate with the use of very small radiators and under-sized pipework.
The efficiencies and emissions of this type of system is very poor. Unfortunately wedo find this type of design throughout the domestic heating industry and frustratingly they are still very prevalent in new build properties.
When assessing a potential ASHP/GSHP installation it is essential the wholesystem is thor-oughly viewed. Heat pumps do require greater and correctlydesigned flow volume. Surface areas of radia-tors are also increased to deliver the correct amount of energy from the heat pump to the room.
This is most important in retrofit installations. Heating systems with poor flow,heat emitter limitations and problematic heat losses must be pinpointed. Whereshort falls in these areas are exposed, a suitable design upgrade will be required. Itwill be necessary to upgrade the sections of the heating system to meet the new design criteria.
It is quite common increase in pipe size, pipe layout and replacing the existingradiators. On average increasing radiators by 2/3rds the size/heat capacity.
With the above in mind UFH and radiator mix will work.
The ‘Efficiency’ of heat pumps is measured by the coefficient of performance(COP). So a COP of 3 means the heat pump produces 3 units of heat energy forevery 1 unit of electricity it consumes. It is essential to design the system so the COP ratio sits in the high or best COP range. (3.5 and higher)
With energy cost figures currently around 1KW of electric is £0.14 gas @ £0.04.
the above is imperative to meet the correct COP (14 divided by 3.5= 4)
We show the need to meet the COP of 3.5 to break even in running costs.
With a lower COP the costs of running the system will be higher than gas whichwill increase operating costs.
The COP is the efficiency when operating at certain temperatures. This will varyover the seasons. The SPF is a measure of the total annual heat delivered from asystem compared to the total energy input to run the system. If electricsupplementary back-up heaters are included, then the SPF must include this. Italso includes any fans and pumps on the system.
The actual SPF of a system (heat-meter output reading divided by the electric inputmeter) will be greatly affected by the whole system and the way that it is operated.
If you want the highest SPF, it is more important to focus on the design and mode ofopera-tion rather than to get too hung up on the rating of the unit.
Ideally a heat pump will not need to generate the high temperature that often. Forhot water production it is essential and heat pumps are more than capable ofreaching temperatures over 65C and in hot water mode for short periods that isacceptable. But definitely not for space heating
A good solution to support this theory reduce the lower COP running times is toutilise Solar Thermal. This simple and extremely effective technology can take up60% of hot water requirements for the year. Thus reducing the high temp required and reducing energy consumption and costs.
