scholarly journals Large-scale heat pumps in sustainable energy systems: System and project perspectives

2007 ◽  
Vol 11 (3) ◽  
pp. 143-152 ◽  
Author(s):  
Morten Blarke ◽  
Henrik Lund
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Heat Production ◽  
Large Scale ◽  
Energy System ◽  
Heat Pumps ◽  
Production Costs ◽  
Coefficient Of Performance ◽  
Operational Mode ◽  
Temperature Heat

This paper shows that in support of its ability to improve the overall economic cost-effectiveness and flexibility of the Danish energy system, the financially feasible integration of large-scale heat pumps (HP) with existing combined heat and power (CHP) plants, is critically sensitive to the operational mode of the HP vis-?-vis the operational coefficient of performance, mainly given by the temperature level of the heat source. When using ground source for low-temperature heat source, heat production costs increases by about 10%, while partial use of condensed flue gasses for low-temperature heat source results in an 8% cost reduction. Furthermore, the analysis shows that when a large-scale HP is integrated with an existing CHP plant, the projected spot market situation in The Nordic Power Exchange (Nord Pool) towards 2025, which reflects a growing share of wind power and heat-supply constrained power generation electricity, further reduces the operational hours of the CHP unit over time, while increasing the operational hours of the HP unit. In result, an HP unit at half the heat production capacity as the CHP unit in combination with a heat-only boiler represents as a possibly financially feasible alternative to CHP operation, rather than a supplement to CHP unit operation. While such revised operational strategy would have impacts on policies to promote co-generation, these results indicate that the integration of large-scale HP may jeopardize efforts to promote co-generation. Policy instruments should be designed to promote the integration of HP with lower than half of the heating capacity of the CHP unit. Also it is found, that CHP-HP plant designs should allow for the utilization of heat recovered from the CHP unit?s flue gasses for both concurrent (CHP unit and HP unit) and independent operation (HP unit only). For independent operation, the recovered heat is required to be stored. .

scholarly journals New Low-Temperature Central Heating System Integrated with Industrial Exhausted Heat Using Distributed Electric Compression Heat Pumps for Higher Energy Efficiency

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6582
Author(s):  
Fangtian Sun ◽  
Yonghua Xie ◽  
Svend Svendsen ◽  
Lin Fu
Keyword(s):  
Energy Efficiency ◽  
Low Temperature ◽  
Heat Source ◽  
Thermal Performance ◽  
Heating System ◽  
Heat Pumps ◽  
Payback Period ◽  
Coefficient Of Performance ◽  
Financial Benefit ◽  
Central Heating

Industrial exhausted heat can be used as the heat source of central heating for higher energy efficiency. To recover more industrial exhausted heat, a new low-temperature central heating system integrated with industrial exhausted heat using distributed electric compression heat pumps is put forward and analyzed from the aspect of thermodynamics and economics. The roles played by the distributed electric compression heat pumps in improving both thermal performance and financial benefit of the central heating system integrated with industrial exhausted heat are greater than those by the centralized electric compression heat pumps. The proposed low-temperature central heating system has higher energy efficiency, better financial benefit, and longer economical distance of transmitting exhausted heat, and thus, its configuration is optimal. For the proposed low-temperature central heating system, the annual coefficient of performance, annual product exergy efficiency, heating cost, and payback period are about 22.2, 59.4%, 42.83 ¥/GJ, and 6.2 years, respectively, when the distance of transmitting exhausted heat and the price of exhausted heat are 15 km and 15 ¥/GJ, respectively. The economical distance of transmitting exhausted heat of the proposed low-temperature central heating system could approach 25.1 km.

scholarly journals Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1853 ◽  
Author(s):  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Heat Sources ◽  
Ground Heat Exchangers ◽  
Temperature Heat

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.

scholarly journals Evaluating the Potential Contribution of District Heating to the Flexibility of the Future Italian Power System

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 584
Author(s):  
Chiara Magni ◽  
Sylvain Quoilin ◽  
Alessia Arteconi
Keyword(s):  
Power Systems ◽  
Power System ◽  
Large Scale ◽  
District Heating ◽  
Energy System ◽  
Heat Pumps ◽  
Electricity Sector ◽  
Potential Contribution ◽  
The Future ◽  
Promising Solution

Flexibility is crucial to enable the penetration of high shares of renewables in the power system while ensuring the security and affordability of the electricity dispatch. In this regard, heat–electricity sector coupling technologies are considered a promising solution for the integration of flexible devices such as thermal storage units and heat pumps. The deployment of these devices would also enable the decarbonization of the heating sector, responsible for around half of the energy consumption in the EU, of which 75% is currently supplied by fossil fuels. This paper investigates in which measure the diffusion of district heating (DH) coupled with thermal energy storage (TES) units can contribute to the overall system flexibility and to the provision of operating reserves for energy systems with high renewable penetration. The deployment of two different DH supply technologies, namely combined heat and power units (CHP) and large-scale heat pumps (P2HT), is modeled and compared in terms of performance. The case study analyzed is the future Italian energy system, which is simulated through the unit commitment and optimal dispatch model Dispa-SET. Results show that DH coupled with heat pumps and CHP units could enable both costs and emissions related to the heat–electricity sector to be reduced by up to 50%. DH systems also proved to be a promising solution to grant the flexibility and resilience of power systems with high shares of renewables by significantly reducing the curtailment of renewables and cost-optimally providing up to 15% of the total upward reserve requirements.

scholarly journals Effect of Heat Demand on Integration of Urban Large-Scale Renewable Schemes—Case of Helsinki City (60 °N)

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2164
Author(s):  
Vahid Arabzadeh ◽  
Peter D. Lund
Keyword(s):  
Wind Power ◽  
Large Scale ◽  
Energy Use ◽  
Energy Systems ◽  
Energy System ◽  
Heat Pumps ◽  
Electricity Production ◽  
Population Increase ◽  
Building Energy Efficiency ◽  
Heat Demand

Heat demand dominates the final energy use in northern cities. This study examines how changes in heat demand may affect solutions for zero-emission energy systems, energy system flexibility with variable renewable electricity production, and the use of existing energy systems for deep decarbonization. Helsinki city (60 °N) in the year 2050 is used as a case for the analysis. The future district heating demand is estimated considering activity-driven factors such as population increase, raising the ambient temperature, and building energy efficiency improvements. The effect of the heat demand on energy system transition is investigated through two scenarios. The BIO-GAS scenario employs emission-free gas technologies, bio-boilers and heat pumps. The WIND scenario is based on large-scale wind power with power-to-heat conversion, heat pumps, and bio-boilers. The BIO-GAS scenario combined with a low heat demand profile (−12% from 2018 level) yields 16% lower yearly costs compared to a business-as-usual higher heat demand. In the WIND-scenario, improving the lower heat demand in 2050 could save the annual system 6–13% in terms of cost, depending on the scale of wind power.

scholarly journals Achieving a Flexible and Sustainable Energy System: The Case of Kosovo

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4753 ◽  
Author(s):  
Njomza Ibrahimi ◽  
Alemayehu Gebremedhin ◽  
Alketa Sahiti
Keyword(s):  
Carbon Capture ◽  
Large Scale ◽  
Sustainable Energy ◽  
Supply And Demand ◽  
Energy System ◽  
Heat Pumps ◽  
Operating Efficiency ◽  
Baseline Scenario ◽  
Renewable Sources ◽  
Sustainable Energy System

In today’s energy system, the diffusion of renewable-based technologies is accelerating rapidly. Development of mechanisms that support the large-scale deployment of renewables towards global warming and climate change mitigation continues to remain an issue of utter importance. The most important challenges the energy system of Kosovo faces today is the difficulty to meet all the demand for electricity, low operating efficiency and high release of greenhouse gas emissions, but specifically a large source of carbon dioxide (CO2). Consequently, this influences not only the stability of the system but the society as a whole. This paper addresses several possibilities for designing an adaptable energy system in Kosovo with the ability to balance electricity supply and demand which will meet the requirements for a more efficient, reliable and secure system. A new way of energy generating through integration of new renewable and non-renewable technologies is developed using the EnergyPLAN model. The system is based on available technologies: existing hydro, wind, photovoltaic (PV), combined heat and power (CHP) and new solar thermal, heat pumps and biomass. The baseline scenario 2015 was expanded by four additional scenarios, two for the year 2030 and two for the year 2050. The contribution of renewable sources in the primary energy supply (PES) in the performed scenarios was 14.8%, 34.1%, 38.4%, 69.7% and 68.3% respectively. Further, a very important component of this paper is the investigation of integrating carbon capture and sequestration (CCS) technology in the coal-based power plant as part of the analysis in the second scenario for 2050. The shift to zero-carbon energy system in Kosovo requires additional research and assessment in order to identify the untapped potential of renewable sources. However, from the results obtained it can be concluded that the goal of a secure, competitive and sustainable energy system in Kosovo state which will meet its long-term energy needs can be certainly achieved.

scholarly journals Time series of heat demand and heat pump efficiency for energy system modeling

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Oliver Ruhnau ◽  
Lion Hirth ◽  
Aaron Praktiknjo
Keyword(s):  
Time Series ◽  
System Modeling ◽  
Energy System ◽  
Heat Pumps ◽  
Reanalysis Data ◽  
Coefficient Of Performance ◽  
Pump Efficiency ◽  
Water Heating ◽  
Heat Demand ◽  
Energy System Modeling

Abstract With electric heat pumps substituting for fossil-fueled alternatives, the temporal variability of their power consumption becomes increasingly important to the electricity system. To easily include this variability in energy system analyses, this paper introduces the “When2Heat” dataset comprising synthetic national time series of both the heat demand and the coefficient of performance (COP) of heat pumps. It covers 16 European countries, includes the years 2008 to 2018, and features an hourly resolution. Demand profiles for space and water heating are computed by combining gas standard load profiles with spatial temperature and wind speed reanalysis data as well as population geodata. COP time series for different heat sources – air, ground, and groundwater – and different heat sinks – floor heating, radiators, and water heating – are calculated based on COP and heating curves using reanalysis temperature data. The dataset, as well as the scripts and input parameters, are publicly available under an open source license on the Open Power System Data platform.

A Totally Heat-Driven Refrigeration System Using Low-Temperature Heat Sources for Low-Temperature Applications

2019 ◽  
Vol 27 (02) ◽  
pp. 1950012 ◽  
Author(s):  
Zeynab Seyfouri ◽  
Mehran Ameri ◽  
Mozaffar Ali Mehrabian
Keyword(s):  
Low Temperature ◽  
Heat Source ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Refrigeration Cycle ◽  
Water Mixture ◽  
Refrigeration System ◽  
Power Requirement ◽  
Temperature Heat

In the present study, a totally heat-driven refrigeration system is proposed and thermodynamically analyzed. This system uses a low-temperature heat source such as geothermal energy or solar energy to produce cooling at freezing temperatures. The proposed system comprises a Rankine cycle (RC) and a hybrid GAX (HGAX) refrigeration cycle, in which the RC provides the power requirement of the HGAX cycle. An ammonia–water mixture is used in both RC and HGAX cycles as the working fluid. A comparative study is conducted in which the proposed system is compared with two other systems using GAX cycle and/or a single stage cycle, as the refrigeration cycle. The study shows that the proposed system is preferred to produce cooling at temperatures from 2∘C to [Formula: see text]C. A detailed parametric analysis of the proposed system is carried out. The results of the analysis show that the system can produce cooling at [Formula: see text]C using a low-temperature heat source at 133.5∘C with the exergy efficiency of about 20% without any input power. By increasing the heat source temperature to 160∘C, an exergy efficiency of 25% can be achieved.

scholarly journals Energy Analysis of a Novel Ejector-Compressor Cooling Cycle Driven by Electricity and Heat (Waste Heat or Solar Energy)

2020 ◽  
Vol 12 (19) ◽  
pp. 8178
Author(s):  
Fahid Riaz ◽  
Kah Hoe Tan ◽  
Muhammad Farooq ◽  
Muhammad Imran ◽  
Poh Seng Lee
Keyword(s):  
Low Temperature ◽  
Thermal Energy ◽  
Waste Heat ◽  
Solar Thermal ◽  
Coefficient Of Performance ◽  
Condensation Temperature ◽  
Low Grade ◽  
Solar Thermal Energy ◽  
Temperature Heat ◽  
Vapour Compression

Low-grade heat is abundantly available as solar thermal energy and as industrial waste heat. Non concentrating solar collectors can provide heat with temperatures 75–100 °C. In this paper, a new system is proposed and analyzed which enhances the electrical coefficient of performance (COP) of vapour compression cycle (VCC) by incorporating low-temperature heat-driven ejectors. This novel system, ejector enhanced vapour compression refrigeration cycle (EEVCRC), significantly increases the electrical COP of the system while utilizing abundantly available low-temperature solar or waste heat (below 100 °C). This system uses two ejectors in an innovative way such that the higher-pressure ejector is used at the downstream of the electrically driven compressor to help reduce the delivery pressure for the electrical compressor. The lower pressure ejector is used to reduce the quality of wet vapour at the entrance of the evaporator. This system has been modelled in Engineering Equation Solver (EES) and its performance is theoretically compared with conventional VCC, enhanced ejector refrigeration system (EERS), and ejection-compression system (ECS). The proposed EEVCRC gives better electrical COP as compared to all the three systems. The parametric study has been conducted and it is found that the COP of the proposed system increases exponentially at lower condensation temperature and higher evaporator temperature. At 50 °C condenser temperature, the electrical COP of EEVCRC is 50% higher than conventional VCC while at 35 °C, the electrical COP of EEVCRC is 90% higher than conventional VCC. For the higher temperature heat source, and hence the higher generator temperatures, the electrical COP of EEVCRC increases linearly while there is no increase in the electrical COP for ECS. The better global COP indicates that a small solar collector will be needed if this system is driven by solar thermal energy. It is found that by using the second ejector at the upstream of the electrical compressor, the electrical COP is increased by 49.2% as compared to a single ejector system.

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