Figure 2 CHP plant and electric boiler, Vestforbrænding, Greater Copenhagen How to fit a 40 MW electric boiler into an existing 33 MW gas-fuelled CC CHP plant The 33 MW CHP plant and the 40 MW electric boiler owned by Vestforbrænding is a perfect match, generating 33 MW of heat at high prices and 40 MW of heat at low prices to be stored in the 8,000 m3 pressure-less heat storage tank. Besides, the plant can regulate up and down and thereby stabilize the power grid.
boiler, e.g., with a capacity equal to the electric capacity of the CHP plant or the maximal capacity of the cable to the plant. In that case, the system has been upgraded to a 3rd generation DH system. This opens up the following benefits: The electric boiler utilizes “surplus” renewable electricity and reduces curtailment of wind and solar, e.g., loading the thermal storage tank with cheap electricity, which other- wise would be curtailed.
The electric boiler can be interrupted at any time in case of capacity problems in the electric grid.
The electric boiler can deliver down-regulation services to the ancillary service markets fast and efficiently in combina- tion with the thermal storage tank. The electric boiler can, combined with the storage, the CHP plant, and backup boilers, deliver more cost-effective, low carbon peak and spare capacity to the district heating system. This system will positively impact the power grid and its ability to integrate renewable electricity. It can operate even in case the buildings connected to the district heating system need high temperatures for heating. However, some heat may still be generated by gas/oil boilers if neither the electric boiler nor the CHP is competitive over a long period. 4th generation district heating In case the buildings have lowered the return temperature, and the need for a high supply temperature, the district heat- ing system can reduce the supply temperature and install efficient heat pumps and thereby be upgraded to what we call the final 4th generation district heating system. Thereby all heat can be generated by an optimal combination of CHP, electric boilers, heat pumps, and boilers. If the storage capaci- ty is optimized, the boilers will deliver large capacities but only generate a minor part of the heat energy. The boilers will serve as a vital backup capacity for the wind and solar, much cheap- er than a natural gas turbine. Yet, as we all understood during the energy crisis, natural gas turbines are of high value to the electricity system, albeit they have very few operating hours for the security of supply reasons. 4th generation district heating and cooling District cooling (DC) can develop from 1st to 4th generation cooling and complement the 4th generation DH forming a DH&C system. This 4th generation DH&C system is a further natural development in case there is a significant demand for comfort cooling and process cooling.
A DC network and a chilled water tank benefit from econo- my of scale and replace expensive and inefficient individual building-level chillers. The chilled water tank levels the consumption and opens for optimal operation of chillers in response to the electricity prices.
The heat pump will generate combined heating and cooling to the 4th generation DH and the 4th generation DC grids.
Some ambient energy sources, e.g., drain water, groundwa- ter, or wastewater, can provide ambient heat to the heat pump for heating in winter and ambient cold to the heat pump for cooling in summer.
To some extent, groundwater with two interconnected wells can store ambient cold and warm energy interseason.
Made with FlippingBook - Online magazine maker