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Heat Pumps – new trends in low emission home heating

31 May 2011 | Author: Danfoss
Using renewable energy sources instead of fossil fuels is one of the sustainable solutions being undertaken, in our industry, with the aim of solving the energy challenges we face now and in the future. A renewable energy source, the sun generates large amounts of energy which is stored in the air, bedrock, the ground, rivers and lakes. A heat pump collects and extracts the heat from geothermal, aerothermal and hydrothermal sources, warms it up and “pumps” it into our homes to heat our living spaces and water. With a heat pump installed we can help reduce our impact on the environment.
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Chapter 1. Main energy sources for heat pumps
There are 4 main energy sources for heat pumps being bedrock, ground, groundwater and air. With groundwater and air heat pumps being the easiest to install. Ground heat pumps require a large area to lay the pipes and performance can be affected by ground conditions and bedrock heat pumps require the drilling of a bore hole through bedrock.
Chapter 2. Groundwater

A groundwater heat pump uses groundwater to collect energy. The water is pumped up through a water borehole to a heat exchanger, where the energy is recovered. Then the water is discharged back through a second borehole and back into the well.


Benefits:

• Groundwater has a high even temperature year round
• Cooling is possible

Chapter 3. Air
                            



Air heat pumps use energy from the surrounding air. These heat pumps are easy to install and do not require digging or drilling, which makes them very attractive for the large renovation market.


Benefits:

• Easy to install
• Lower investment cost
• No visual or physical impact on the ground
• Large garden area not needed
Chapter 4. A growing market
The residential housing stock in Europe is characterised by aging buildings. Most of these houses use fossil fuels (oil or gas) to heat a water-based heating system, or boiler. When the boilers reach the end of their working life, they need to be replaced and this offers consumers a great opportunity to install a non-fossil fuel heating system instead.
Chapter 5. Policy level
More and more decision makers – from politicians to house owners – are aware of heat pump technology and include it in their heating system recommendations. Acknowledged as an effective way of reducing our reliance on finite primary energy sources, heat pumps are gaining a strong foothold in the market. The European Parliament recognize heat pumps as a technology that uses renewable resources (RES Directive). However only heat pumps with an efficiency or seasonal performance factor (SPF) over 2.875 will contribute to a reduction in the use of primary fossil energy sources.

The SPF is calculated by taking away the energy consumed by the heat pump from the total usable heat. These calculations are based on an average effeciency of electricity generation for the 27 EU states.

In some countries tax credits are available to consumers who install heat pumps that meet specific energy efficiency improvements. As an example in the US, the criteria for ground/air heat pump efficiency improvements over three years are:



 In addition to these minimum efficiency 
 requirements, heat pumps must include a 
 de-superheater, or an integrated 
 water heating system.
Chapter 6. Refrigerants
Today, heat pumps mainly use HCFC and HFC refrigerants. Discussions about the environmental impact of HCFC´s and HFC´s, as well as opportunities for further improvements in efficiency and application range, are likely to push the use of natural refrigerants in this application in the future. Danfoss has a range of products, such as expansion devices, electronic controllers, Performer® Scroll compressors, and brazed plate heat exchangers, which are ideal for heat pump systems. Every scroll reaches an efficiency maximum when the unit is operating at a certain pressure ratio. This is the compressors optimization point. The compressor can be operated at different pressure ratios, but the efficiency will decrease the further the operating conditions differ from the optimisation point (see diagram). Many heat pumps are equipped with scroll compressors. The diagram below shows a typical efficiency curve of a scroll compressor.
Chapter 7. Scroll compressor efficiency and pressure ratio curve
Heat pumps are most efficient when they operate under conditions close to the optimisation point. However, operating conditions – especially for air heat pumps and radiator systems – vary throughout the year. In these cases, the heat pump often needs to operate under conditions quite far away from the optimization point, which causes reductions in efficiency. Danfoss’ HHP compressor has an improved efficiency curve due to the innovative use of the three reed valves.
Chapter 8. Heat pumps a brighter future



It is estimated that over the next 30 years new technologyrelated business opportunities in the heat pump market will be worth tens of trillions of dollars. Danfoss is helping heat pump manufacturers around the globe meet and exceed present – and future – minimum efficiency requirements for heat pump equipment. And our energy-saving, dedicated products and application expertise is helping build business opportunities.

And for end-users, Danfoss products are helping reduce heating costs, fossil fuel dependence, and the carbon footprint of space heating. In addition, Danfoss components are helping heat pump manufacturer’s products reach performance levels that allow consumers to apply for subsidies when buying heat pumps.


 Figure 1


 Figure 2

In figure 1 the standard compressor can operate at different pressure ratios, but efficiency decreases when the operating conditions differ from the optimisation point. – Danfoss now offers a solution to this issue with the use of three read valves, Figure 2.

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