Table 5 shows the influence of the various alternatives on the most important parameters. It is thought that the steam is drained by the upstream turbine, although there are better alternatives for this. It is assumed that all cooling will be taken by dry coolers, although specific solutions must be prepared for the days when the outside temperature is too high.

It is assumed that the waste incinerator has installed full cooling capacity. If waste heat from the capture plant to the DH grid is to be recovered, all the heat that can be sent directly to the DH return from the capture plant should have first priority and be the base load.

It may be interesting to explore actions in existing waste incineration plants, especially flue gas recycling. Oxygen incineration plants are becoming an alternative to other carbon capture technologies and have been considered more closely in L2. If increased flue gas recycling can be done in existing waste incineration plants without major impacts on the downstream process, this is recommended.

The heat supply to the carbon capture plant should come from the steam produced in boilers from the flue gases and not from steam-producing heat pumps on the cooling water of the capture plant. The ideal is if you can take as much steam as possible from existing outlet in the existing turbine and the rest from the upstream turbine if the turbine does not have outlet. If this is not possible, one should take all the steam upstream of the existing steam turbine and possibly install a new smaller counter pressure turbine rather than letting all the steam go through the existing turbine and using steam fans. If the plant does not have steam or hot water available, and the alternative is an electric boiler, a steam-producing HP should be considered.

For recovery of waste heat to the DH network, they should collect as much heat as possible directly from the capture plant to the DH return, this is assumed in Table 5. The remaining waste heat recovery is best done through a heat pump that delivers to the DH return. This can be done with a COP of 6.5 with HFO-based heat pumps or NH3-based heat pumps. We go from delivering 5 MWel (or 40 GWh/year) to the grid without a carbon capture plant to consuming 1-1.5 MWel (or about 10 GWh/year) from the grid with a carbon capture plant and heat pump. If one is to increase DH delivery, the potential is to increase DH delivery maximum 44.9 MW or 45.9 MW, as shown in Figure 55 and Figure 59. Such a heating system would in the best case have a COP of approx. 3.5 and it should be assessed against the remaining peak load sources in the grid together with the DH owner.

For less traditional solutions for recovery of waste heat for DH, it is recommended to look at hybrid heat pumps, CO2 heat pumps, Helium Stirling heat pumps, Rotary vane compressors. These can potentially have a lower power consumption than compressor based HFO or ammonia heat pumps. Several of the less widespread heat pumps listed here have less competition between suppliers and opportunities for innovation support.

Absorption heat pumps are dependent on the DH network not having too high an outlet temperature and that the steam available has a high enough pressure (min. 4 bar(g)). It is worth investigating the possibilities with suppliers of absorption heat pumps to supply a unit that can act as a heat pump in winter and cooler in summer. This could potentially kill two birds with one stone but will probably need to be designed for the application by the supplier. 

To ensure that an installed HP does not experience excessive fluctuations in the process, it is recommended to accumulate heat over short periods, either in the DH network by raising the outlet temperature (and possibly the return temperature) or in a separate accumulation tank. If this is not possible, it is recommended to place newly installed HP as base load during periods when heat demand fluctuates in such a way that it would require heat pumps to be turned on and off frequently.

The waste heat that cannot be utilized is best if you find applications for, this is challenging due to the low temperatures. You may want to look towards nearby businesses for alternative consumers of waste heat.

To cool away unused waste heat, it is a good idea to see if you can cool against the sea either directly or through the DH network. For short periods, it may be wise to use the DH network as cooling. For those days when temperatures are too high for cooling against the outside air, it may also be worthwhile to look at the possibilities of sorptive cooling or an absorption cooler. Most capture plants will require temperatures that make it favorable to have dry coolers with air and any extra capacity for days when it is warmer than the cooling water outside.