Large Heat Pumps in District Heating Systems

Would you believe that District Heating is a century-old system? Now that the technology is well established, the world needs to optimize it for cost-effective use. One means of taking advantage of this solution is to exploit sustainable energy resources optimally.

Customers are also looking for value. For any District Heating system to be worth it, it must be efficient, intelligent, and reliable. District Heating clients want an assurance that the system offers sufficient heat. Second, the system must be affordable, and finally, they want a system that is easy to monitor, control, and optimize.

Utility providers need to reduce CO2 footprint to match the decarbonizing objectives using alternative heat generation technologies as biomass boilers, electric boiler, and electric heat pump to combine it with renewable energies.

At ARANER, we use an array of technologies to help achieve these core needs. From our portfolio of industrial heat pumps, we have large scale heat pumps that help get the job done. In the goal of decarbonizing the District Heating market as much as possible, we believe that heat pumps are the ideal technology.

Heat Pump Technology Explained

A heat pump is a device that uses an external energy source to pump heat from a low energy source to a high-temperature source. It is in the large-scale category if it has a capacity of at least 1000 kW. The range of heat pumps is large depending on the technology employed; with centrifugal compressor type, the range could go to as much as 30 MW. These heat pumps are capable of delivering 100°C heat.

Large heat pumps in DH systems can be very energy efficient, hence excellent in the reduction of energy costs when the difference between the heat source and the heat sink temperature is low.

As indicated in Figure 1 below, the heat pump has a refrigerant for heat absorption in the evaporator and heat release in the condenser. Efficient thermal transfer is promoted by the flow of refrigerant through the closed system.

heat-pump-cycle

Fig 1: Heat Pump Cycle (source: https://industrialheatpumps.nl/en/how_it_works/)

The vapor compression cycle comprises a condenser, compressor, expansion valve, and evaporator. The refrigerant circulates through these components.

The absorption cycle is powered by thermal energy and utilizes the water-absorbing capability of salt or liquids. The characteristic of this technology is the combination of working fluid and absorbent, with popular pairings being water/ammonia and Lithium bromide/water. The solution circuit composed of an absorber, expansion valve, solvent pump, and thermal compressor compresses the working fluid.

In the industry, the older vapor-compression heat pump tends to be more popular than the absorption cycle heat pump.

District Energy reference book

 

Large Heat Pumps are a Perfect Fit

Large-scale heat pumps can enhance low-grade heat to substantial heat for efficient and reliable application in District Heating systems. These pumps are capable of creating the ideal balance and integration across energy systems. They easily provide customers with heating from locally available sources such as groundwater, lake/river/seawater, or any waste heat available. That is essentially the reason why this technology is increasing in popularity globally.

With an electrical heat pump, a DH system can reduce its energy consumption significantly. It is also an effective technology for stabilizing energy prices. A water-to-water heat pump is also popular for its ability to capture heat from a waste energy source, producing hot water at a higher temperature and use it for District Heating. If a cooling demand is simultaneous with the heating one, the COP system will increase significantly the efficiency of a district cooling & heating system.

Heat pumps are even relevant when you look at the future setting of cities. The future of conventional cities is going to be hectic unless we can solve the spatial disparity between heat demand and supply. It is often difficult to prevent energy wastage owing to this difference. The smart city concept was introduced to overcome such challenges through integration, interconnection, and accumulation of different systems. When used with heat storage feature, large-scale heat pumps can answer to prudent energy management in smart cities.

Do not worry if your DH system is already up and running. Large heat pumps can integrate with existing infrastructure. You could install it as an add-on or simply opt for stand-alone mode. Let our experts know your preferred design and they will offer something ideal for your needs.

Choosing the Best Heat Pump for DH

When considering the best large heat pumps in District Heating systems, the heat sources must be abundant. Common sources for these components are raw sewage water, groundwater, and surface water.

Specific investment costs and high COP are requirements for a large heat pump, even for part load operation. This means that the device should be designed for baseload operation. Peak load can be derived from other sources such as electro-boilers and gas/oil-fired boilers.

The working fluid for large-scale heat pumps is HFC as R134a or HFO as R1234ze and in some cases also ammonia (R717). Ammonia is only possible to be used for screw compressor heat pump technology. A two-stage design is the best option, as it maintains acceptable levels of temperatures for the lube oil system and discharge refrigerant temperature, and enhances system performance.

Apart from having a high COP, the working fluid in the large-scale heat pump for DH should have zero or low GWP to be an eco-friendly solution.

Depending on local regulation limitations, ARANER can design a large-scale heat pump with the most suitable refrigerant.

Conclusion

Large heat pump technology integrates with the District Heating system perfectly since it relies on waste heat sources at low cost, thus reducing greenhouse gas emissions and overreliance on primary energy sources. Boiler systems are nowhere near the heat pump regarding these valuable benefits. With an outlet temperature capability of as much as 90ºC-100ºC, the heat pump can even support high-temperature DH systems.

The actual trend for 5th generation District Heating will be the reduction of flow temperature supply to around 60ºC to achieve even a more efficient network.

If you need security, flexibility, and efficiency like never before for your DH system, inquire about our heat pumps here.

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