Researchers in Denmark have discovered that utilizing a big air-to-water warmth pump to warmth a photo voltaic district can considerably cut back the extent of its warmth prices. The proposed system configuration was simulated for an current district heating plant in Denmark and located to enhance the system’s flexibility in response to power costs.
Researchers on the Technical University of Denmark are investigating how giant air-to-water warmth pumps will be mixed with PV-powered district heating techniques with the intention of lowering levelized warmth prices and enhancing flexibility. within the system. They defined that air-to-water warmth pumps have the power to generate and retailer warmth in tanks when electrical energy costs are low, permitting using saved heating throughout excessive electrical energy costs.
The proposed methodology is simulated by TRNSYS software program in an current solar-assisted district heating system within the Danish metropolis of Ørum. The system consists of a ground-mounted photo voltaic thermal plant, a 2.5 MW warmth pump, a gasoline boiler, and a vertical cylindrical scorching water tank of 1,000 m3.
“In this method, the warmth pump performs a dominant position in a altering power market because of its flexibility in cooperation with the boiler,” the scientists defined. “The medium to low temperature water within the tank can warmth the refrigerant earlier than it enters the compressor, thus rising the coefficient of efficiency (COP) of the warmth pump. Therefore, the warmth pump is anticipated to enhance the compatibility of kit and the flexibleness of the heating system.
The group assumed that the system will function between 2020 and 2022 and decided that it operates with out the warmth pump within the first yr, whereas the second and third years embody it. The 6,355 m2 photo voltaic thermal plant can meet the warmth demand through the summer time, however within the winter gasoline boiler is required to satisfy the better demand. The tank will be operated in several methods to chop warmth manufacturing and demand.
Image: Technical University of Denmark, Renewable Energy, Common License CC BY 4.0
The warmth pump is believed to make use of ammonia as a refrigerant and depend on a screw compressor and a piston compressor. The outlet temperature is proven at 67 C.
“An economizer is included to boost the temperature of the refrigerant earlier than it enters the compressor,” the group emphasised. “This enchancment results in a discount in electrical energy consumption, as a result of the compressor maintains the required outlet temperature extra effectively in comparison with a warmth pump system with out an economizer.”
The techno-economic evaluation carried out by the scientists confirmed that the economizer was capable of enhance the warmth pump COP from 3.33 to three.53 with an ambient temperature of lower than 5 C. It additionally confirmed that the levelized warmth price of the system improved. as much as 19% in 2021 and 37% in 2022.
“The warmth manufacturing of the warmth pump decreases whereas the electrical energy costs rise to an appropriate stage,” defined the group. “If the spot value of electrical energy exceeds a sure threshold, the warmth pump will shut down, and the boiler will develop into the primary auxiliary heater.”
The evaluation additionally exhibits that the annual seasonal COP of the system elevated from 1.22 to 2.62 through the 3-year time-frame of the simulation.
“However, the coupling impact of the warmth pump and its financial system solely barely improves the effectivity of the photo voltaic collector and the warmth pump itself,” the teachers stated. “Replacing the air-source warmth pump with a water-to-water warmth pump can decrease the return water temperature within the SC subject, which is anticipated to enhance the effectivity of the SC.”
System particulars are below examine”Thermo-economic evaluation of photo voltaic district heating plant with air-to-water warmth pump,” printed in Renewable Energy.
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