A heat pump is a device which can take waste heat and increase its temperature to higher, more useful temperature, thereby reducing the amount of energy needed to provide the useful heat.
APPLICATIONS FOR HEAT PUMPS
Heat pumps can be used for a range of industrial, commercial and residential applications, for providing both heating and cooling.
Heat pumps can supply process heat for all kinds of industrial processes, with the type of heat pump used depending on the heat being recovered and the temperature of delivered heat required. Until recently, heat pumps were only considered viable for lower (less than 120 °C) temperatures, however, that temperature range is increasing with high temperature heat pumps now being developed and tested for high-heat applications such as drying of building products.
HOW HEAT PUMPS WORK
Heat pumps are a class of active heat-recovery equipment that allows the temperature of a waste-heat stream to be increased to a higher, more useful temperature.
Among the different types of heat pumps that have been developed, the mechanical heat pump is the most widely used. Its operating principle is based on compression and expansion of a working fluid, or so called 'refrigerant'. A heat pump has four main components: evaporator, compressor, condenser and expansion device. The refrigerant is the working fluid that passes through all these components. In the evaporator heat is extracted from a waste heat source. In the condenser this heat is delivered to the consumer at a higher temperature level.
Electric energy is required to drive the compressor and this energy is added to the heat that is available in the condenser. The efficiency of the heat pump is denoted by its COP (coefficient of performance), defined as the ratio of total heat delivered by the heat pump to the amount of electricity needed to drive the heat pump.
Coefficient of performance - efficiency of refrigeration and heat pumps - Industrialheatpumps.nl
Refrigerants for heat pumps - Industrialheatpumps.nl
TYPES OF HEAT PUMPS
There are a range of heat pump technologies, each with different benefits and suited applications. Two of the most common with a wide range of use are compression heat pumps and mechanical vapour recompression heat pumps.
Mechanical vapour recompression heat pumps
Mechanical vapour recompression (MVR) is an open heat pump system in which the pressure and temperature of the vapour, together with the corresponding saturation temperature, are increased by means of compression (Energy.nl).
This technology is a variant of the heat pumps traditionally used for low-temperature evaporation processes which need only a small – less than 15 °C – temperature lift and typically deliver COPs greater than 10. The technology can deliver heat up to 250 °C but is more commonly used below 100 °C.
Mechanical vapour recompression technology explained. - Howden.com
Compression heat pumps
Compression heat pumps uses a refrigerant in a closed loop. Akin to the reverse cycle air conditioner, an industrial heat pump is effectively a reverse cycle refrigerator. This type of heat pump is typically used for providing lower temperatures.
Other types of heat pumps
A Sabroe DualPAC heat pump from Johnson Controls installed in the Netherlands. Source: Johnson Controls
Transitioning to heat pump technologies - and why it isn't a straight swap
The capital costs of replacing a 2 MW steam boiler with a 2 MW heat pump would be five to eight times that of a boiler and the payback is likely to be greater than five years. However, a heat pump that is 500 kW or smaller is likely to be large enough when replacing a steam system. Here’s how:
First, you need energy use data. It is likely that the 2 MW of heating demand is rarely needed. If 2 MW of heating is only needed for say one hour per day and the rest of the time only 1 MW is needed, you have just halved the size of the heat pump when combined with a thermal battery.
Second, if you calculate the heat losses from the total steam system, it is likely that the overall system is less than 60% efficient. A hot water heat pump system will have heat losses of less than 10% so now you just reduce the required heat pump size further.
Third, if you have waste heat from a refrigeration plant (oil coolers or condenser) you can harness that waste heat to boost the heat pump performance. As a rule of thumb, every 1 °C increase in the heat source used by the heat pump will increase the performance by 3%. So, using 30 °C warm water from the refrigeration plant could deliver a 30% efficiency performance vs using air at 20 °C.
Finally, if you have on-site solar PV or access to electricity spot prices, you may want to increase the size of your heat pump and thermal battery to operate more during the day, when electricity prices are low, and less during the evening when prices are high. This may not even require a larger heat pump to achieve. If the heat pump is sized for the coldest part of the year, then you will likely have spare capacity for more than 10 months so you can run the heat pump only when electricity prices are low.
HEAT PUMP CASE STUDIES
There are more and more examples of heat pumps significantly reducing energy use and emissions in industrial processes by utilising waste heat. Here are some examples from Australia and around the world.
LEARN MORE: HEAT PUMP WEBINARS
The below webinars feature some of the world's foremost experts on industrial heat pumps for process heat. The presentations include the latest technology updates and case studies on technology trials and successful heat pump projects.