Heat pumps

Broad applications for an established technology with development potential

By utilizing thermal gradients, heat pumps can substantially reduce CO2 emissions. Waste heat can be more effectively utilized and industry clusters could use their excess heat to optimze heating, cooling and various production processes. These are only a few examples of the potentials of heat pumps. The technology is well-developed, but needs to be researched still further to work on an industrial scale.

Naturally, heat will by itself flow from a warm to a colder place. Heat pumps possess the unique property, that they may take up heat from a low temperature level and transport it to a higher temperature. To achieve this, we must supply energy, most usual in the form of electricity. The ratio between the heat delivered and the electricity spent, is called the heating factor. Heat pumps may be utilized successfully both in buildings and industry.

Within the building sector we need energy BOTH to supply and remove heat from the rooms to sustain a comfortable indoor temperature around the year, AND to produce hot water for different purposes. Around half of the 80 TWh energy spent in Norwegian buildings is used to support heating demands (40-45 TWh). In their analysis ‘Klimakur’ has calculated that this will increase to 50-55 TWh in 2030.

Technology status

Heat pumps constitute a technology that make it possible to support heating demands in an efficient way, so that we may reduce substantially the energy use for these purposes. Heat pumps makes it possible to gather free of charge renewable heat from the so-called ‘ambient’, that is ambient air, water or underground, and increase the temperature of this heat so much that it may be used within the house for ‘heating’. Likeways the same ‘heat pump’ may be used in summer to transport heat from the indoor rooms and deliver it to the hot outdoor air, so that a comfortable indoor temperature may be sustained (‘climate cooling’).

The electric energy (or work) needed to operate heat pumps is substantially lower than the heat supplied, because most of the heat delivered is collected ‘free of charge’ from the ambient.The ratio between delivered heat Q and the electricity used W, is defined as ‘heating factor’, which is used to represent the efficiency of the heat pump. If the average heating factor is 4 over the season, it means that 75% of the heat delivered to the building is gathered free of charge from the ambient, while 25% come from the electricity used to operate the heat pump. This electricity is converted and utilized by the heat pump.

The heating factor is depending strongly on the temperature difference between the room and the heat source – small temperature difference will give higher heating factor. If we collect heat from cold air, we get the lowest heating factor. If we can gather heat from sea water or underground, where the source temperature is higher, the heating factor will increase. Why technology for heat exchange with the ground receive more attention.

The application of heat pumps in Norway was delayed for specific reasons, but it took off around

whereoff 5-6 TWh was gathered from ambient air and water. Forecasts for 2020 show that heat pumps will deliver around 20 TWh (12 TWh free of charge from the ambient). Thus the ambient will be a substantial renewable energy source in future – also in Norway.

When heat pumps replace electric heating (based on hydropower), valuable electricity will be available for alternative value creating activity; export or inland power refining process industry.

When heat pumps substitute oil or gas fired heating plants (which receive high attention in the Climate Report), this will contribute to reduce CO2-emissions substantially, even when the electricity comes from thermal power stations. Therefore heat pumps constitute an environment-friendly, efficient energy technology both on the national and international market.

Challenges and opportunities

Heat pumps have environmental problems because they used to utilize so-called halocarbons as working fluid. These are produced and supported chemical industry. The ozone-problem (Montreal Protocol) was solved by changing the working fluid from CFC to HFC. However HFCs are strong greenhouse gases that were included in the Kyoto Protocole. In Norway we have made priority to develop technology that utilize so called ‘natural working fluids’ (CO2, NH3 etc.). This strategy was promoted by the late professor Gustav Lorentzen, who also developed a successful patent based on CO2 as working fluid. This technology possesses a large international potential. It could be mentioned that to-day there are almost 4 million tap water heat pumps (‘Eco-Cuto’) for individual houses in Japan based on Norwegian technology, originally brought forward by Hydro Aluminum.

The competence on CO2-technology is strong in Norway. This competence has already been utilized by Norwegian companies that have developed tap water heat pumps for larger houses and for super markets; cooling and heating equipment for cars; refrigeration plants on fishing vessels and several other areas of application.

Heat Pumps may also be utilized to make industrial processes more energy efficient, and make energy available for other purposes. The potential may be substantially increased if we may develop better solutions for high temperature heat pumps; to utilize low temperature waste heat (20 – 100 oC) to cover heat demand at higher temperature (100-200 oC). Solutions based on steam-compression-processes for natural working fluids (CO2, NH3, Hydro Carbons and H2O) could also be developed to produce electricity, based on the competence within CfRE. Further solutions based on absorption and compression-absorption principles should also be investigated.

Another huge possibility is to develop ‘smart energy technology’ for industrial clusters – where energy is utilized by different industries within a local community that may cooperate to provide and share electricity, heating and cooling in a smarter and more efficient way.

R&D recommendations:

• Develop customized applications for heat pumps in the domestic and industrial sectors.

• Develop high temperature heat pumps based on natural working fluids for industrial purposes. policy recommendations:

• Launch an initiative to develop CO2 heat pumps for warm tap water and climatization of future ‘Zero Emission

Buildings.’