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Large-scale heat pumps (HPs) and refrigeration plants are essential technologies to decarbonise the heating and cooling sector. District heating and cooling (DHC) can be supplied with low carbon footprint, if power generated from renewable energy sources is used. The simultaneous supply of DHC is often not considered in energy planning, nor the characteristics of the heat source and sink. Simplified approaches may not reveal the true potential of HPs and chillers. In this paper, different heat sources and sinks and their characteristics were considered for the simultaneous supply of DHC based on large-scale HPs and refrigeration plants. An optimization model was developed based on mixed-integer linear programming. The model is able to identify ideal production and storage capacities, heat sources and sinks based on realistic hourly operation profiles. By doing so, it is possible to identify the most economical or sustainable supply of DHC using electricity. The optimization model was applied to the Nordhavn area, a new development district of Copenhagen, Denmark. The results show that a combination of different heat sources and sinks is ideal for the case study. A HP that uses the district cooling network as a heat source to supply DHC was shown to be very efficient and economical. Groundwater and sewage water HPs were proposed for an economical supply of district heating. The Pareto frontier showed that a large reduction in annual CO2 emissions is possible for a relatively small increase in investments.

Excess heat is present in many sectors, and its utilization could reduce the primary energy use and emission of greenhouse gases. This work presents a geographical mapping of excess heat, in which excess heat from the industry and utility sector was distributed to specific geographical locations in Denmark. Based on this mapping, a systematic approach for identifying cases for the utilization of excess heat is proposed, considering the production of district heat and process heat, as well as power generation. The technical and economic feasibility of this approach was evaluated for six cases. Special focus was placed on the challenges for the connection of excess heat sources to heat users. To account for uncertainties in the model input, different methods were applied to determine the uncertainty of the results and the most important model parameters. The results show how the spatial mapping of excess heat sources can be used to identify their utilization potentials. The identified case studies show that it can be economically feasible to connect the heat sources to the public energy network or to use the heat to generate electricity. The uncertainty analysis suggests that the results are indicative and are particularly useful for a fast evaluation, comparison and prioritization of possible matches. The excess heat temperature and obtainable energy price were identified as the most important input parameters.

In order to investigate options for improving the maintenance protocol of commercial refrigeration plants, two thermoeconomic diagnosis methods were evaluated on a state-of-the-art refrigeration plant. A common relative indicator was proposed for the two methods in order to directly compare the quality of malfunction identification. Both methods were applicable to locate and categorise the malfunctions when using steady state data without measurement uncertainties. By introduction of measurement uncertainty, the categorisation of malfunctions became increasingly difficult, though depending on the magnitude of the uncertainties. Two different uncertainty scenarios were evaluated, as the use of repeated measurements yields a lower magnitude of uncertainty. The two methods show similar performance in the presented study for both of the considered measurement uncertainty scenarios. However, only in the low measurement uncertainty scenario, both methods are applicable to locate the causes of the malfunctions. For both the scenarios an outlier limit was found, which determines if it was possible to reject a high relative indicator based on measurement uncertainty. For high uncertainties, the threshold value of the relative indicator was 35, whereas for low uncertainties one of the methods resulted in a threshold at 8. Additionally, the contribution of different measuring instruments to the relative indicator in two central components was analysed. It shows that the contribution was component dependent.

The paper presents a modelling framework that may be used to plan the integration of large-scale HPs in district heating (DH) areas. By use of the methodology both optimal HP capacities to be installed and optimal choice of heat source to be used during the year are identified by minimizing total cost of ownership including investment and operational costs. The modelling framework uses mixed-integer linear programming and hourly calculations over one year. Seasonal variations of the heat source temperatures, capacity limitations and HP coefficient of performance as well as technical constraints were taken into account. The DH network of Tallinn, Estonia, was used as a case study. Six different heat source types were identified for 13 potential locations of large-scale HPs. The results showed that the integration of large-scale HPs in the DH network of Tallinn is economically feasible. It was found that 122 MW HP capacity could be installed without compromising the operation of sustainable base load units. The heat sources needed for obtaining this solution were sewage water, river water, ambient air, seawater and groundwater. It was further shown that the Lorenz efficiency depends on the variations of heat source temperatures.

Spray-drying facilities are among the most energy intensive industrial processes. Using a heat pump to recover waste heat and replace gas combustion has the potential to attain both economic and emissions savings. In the case examined a drying gas of ambient air is heated to 200 °C yielding a heat load of 6.1 MW. The exhaust air from the drying process is 80 °C. The implementation of an ammonia–water hybrid absorption–compression heat pump to partly cover the heat load is investigated. A thermodynamic analysis is applied to determine optimal circulation ratios for a number of ammonia mass fractions and heat pump loads. An exergoeconomic optimization is applied to minimize the lifetime cost of the system. Technological limitations are imposed to constrain the solution to commercial components. The best possible implementation is identified in terms of heat load, ammonia mass fraction and circulation ratio. The best possible implementation is a 895 kW heat pump with an ammonia mass fraction of 0.82 and a circulation ratio of 0.43. This results in economic savings with a present value of 146,000 € and a yearly CO 2 emissions reduction of 227 ton.

The paper presents a modelling framework that may be used to plan the integration of large-scale HPs in district heating (DH) areas. By use of the methodology both optimal HP capacities to be installed and optimal choice of heat source to be used during the year are identified by minimizing total cost of ownership including investment and operational costs. The modelling framework uses mixed-integer linear programming and hourly calculations over one year. Seasonal variations of the heat source temperatures, capacity limitations and HP coefficient of performance as well as technical constraints were taken into account. The DH network of Tallinn, Estonia, was used as a case study. Six different heat source types were identified for 13 potential locations of large-scale HPs. The results showed that the integration of large-scale HPs in the DH network of Tallinn is economically feasible. It was found that 122 MW HP capacity could be installed without compromising the operation of sustainable base load units. The heat sources needed for obtaining this solution were sewage water, river water, ambient air, seawater and groundwater. It was further shown that the Lorenz efficiency depends on the variations of heat source temperatures.

The paper presents the results of a simulative thermodynamic analysis of a multifuel CHP plant basing on the technological diagram of Avedøre 2. Calculations have been carried out for the operation of Avedøre 2 plant in the district heating mode. Several variants of simulation have been considered, determined by the choice of operation of the respective plants, viz. main boiler fired with natural gas, main and biomass boiler, main boiler and GT plant, joint operation of the main and biomass boiler and GT plant, main boiler (fired with heavy fuel oil or/and wood chips) and biomass boiler and GT plant. For each variants a diagram of iso-fuel curves has been developed, illustrating the variability of useful effects (power output and district heat) at various loads of the CHP steam part. In case of the variant in which the main boiler and GT are in operation with natural gas as fuel the exemplary energy indices were determined.