scholarly journals Integration of Reversible Heat Pumps in Trigeneration Systems for Low-Temperature Renewable District Heating and Cooling Microgrids

2019 ◽  
Vol 9 (15) ◽  
pp. 3194 ◽  
Author(s):  
Urbanucci ◽  
Testi ◽  
Bruno
Keyword(s):  
Low Temperature ◽  
Carbon Dioxide Emissions ◽  
Energy Demand ◽  
Water Distribution ◽  
District Heating ◽  
Energy System ◽  
Heat Pumps ◽  
Energy Technologies ◽  
Heating And Cooling ◽  
Viable Solution

District heating and cooling networks based on trigeneration systems and renewable energy technologies are widely acknowledged as an energy efficient and environmentally benign solution. These energy systems generally include back-up units, namely fossil-fuel boilers and electric chillers, to enhance system flexibility and cover peak energy demand. On the other hand, 4th generation district heating networks are characterized by low-temperature water distribution to improve energy and exergy efficiencies. Moreover, reversible heat pumps are a versatile technology, capable of providing both heating and cooling, alternately. In this paper, the integration of reversible heat pumps as single back-up units in hybrid renewable trigeneration systems serving low-energy micro-district heating and cooling networks is investigated. A detailed modeling of the system is provided, considering part-load and ambient condition effects on the performance of the units. Size and annual operation of the proposed system are optimized in a case study, namely a large office building located in Pisa (Italy), by means of a genetic algorithm-based procedure. A comparison with the conventional trigeneration system is performed in terms of economic and environmental perspectives. Results show that the integration of reversible heat pumps is an economically viable solution capable of reducing by 7% the equivalent annual cost, increasing the installed power of renewables up to 23%, and lowering by 11% carbon dioxide emissions, compared to the energy system with conventional back-up units.

scholarly journals Synthesis and Optimal Operation of Smart Microgrids Serving a Cluster of Buildings on a Campus with Centralized and Distributed Hybrid Renewable Energy Units

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 745 ◽  
Author(s):  
Daniele Testi ◽  
Paolo Conti ◽  
Eva Schito ◽  
Luca Urbanucci ◽  
Francesco D’Ettorre
Keyword(s):  
Renewable Energy ◽  
Combustion Engine ◽  
District Heating ◽  
Energy System ◽  
Primary Energy ◽  
Heat Pumps ◽  
Optimal Operation ◽  
Optimal Control Strategy ◽  
Renewable Energy Technologies ◽  
Energy Technologies

Micro-district heating networks based on cogeneration plants and renewable energy technologies are considered efficient, viable and environmentally-friendly solutions to realizing smart multi-energy microgrids. Nonetheless, the energy production from renewable sources is intermittent and stochastic, and cogeneration units are characterized by fixed power-to-heat ratios, which are incompatible with fluctuating thermal and electric demands. These drawbacks can be partially overcome by smart operational controls that are capable of maximizing the energy system performance. Moreover, electrically driven heat pumps may add flexibility to the system, by shifting thermal loads into electric loads. In this paper, a novel configuration for smart multi-energy microgrids, which combines centralized and distributed energy units is proposed. A centralized cogeneration system, consisting of an internal combustion engine is connected to a micro-district heating network. Distributed electric heat pumps assist the thermal production at the building level, giving operational flexibility to the system and supporting the integration of renewable energy technologies, i.e., wind turbines, photovoltaic panels, and solar thermal collectors. The proposed configuration was tested in a hypothetical case study, namely, a University Campus located in Trieste, Italy. The system operation is based on a cost-optimal control strategy and the effect of the size of the cogeneration unit and heat pumps was investigated. A comparison with a conventional configuration, without distributed heat pumps, was also performed. The results show that the proposed configuration outperformed the conventional one, leading to a total-cost saving of around 8%, a carbon emission reduction of 11%, and a primary energy saving of 8%.

scholarly journals Gas Engine-Driven Heat Pumps for Small-Scale Applications: State-of-the-Art and Future Perspectives

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4845
Author(s):  
Carlo Roselli ◽  
Elisa Marrasso ◽  
Maurizio Sasso
Keyword(s):  
Low Temperature ◽  
District Heating ◽  
Primary Energy ◽  
Heat Pumps ◽  
Small Scale ◽  
Future Perspectives ◽  
Gas Engine ◽  
Heating And Cooling ◽  
Research Activities ◽  
Energy Community

Gas engine-driven heat pumps are an interesting option to satisfy space heating and cooling demands aiming at energy saving, environmental impact and operating costs’ reduction. This work presents (i) a comprehensive review updated on gas engine-driven heat pumps research activities, (ii) the investigation of the central role of this technology in the air conditioning sector and (iii) the future perspectives regarding gas engine heat pumps’ diffusion in the context of the energy sector decarbonisation. The outcomes highlight that gas engine heat pumps could have better environmental performance compared to electric heat pumps both in heating and cooling operations. Moreover, they could play a pivotal role in the fight against climate change and energy security since they can guarantee an energy mix differentiation moving from electricity to natural gas and renewable gases’ usage. Indeed, by 2030, a lower-carbon gas grid could be supported by renewable gases. A further investigation has concerned diffusion of gas heat pumps activated from biofuels produced by local biomass in an energy community scenario based on a low-temperature energy district network. A novel biomass-based GEHP interacting with a low-temperature district heating network is proposed here. This system could save more than 30% of primary energy compared to biomass-fuelled boilers.

scholarly journals 5th generation district heating and cooling systems as a solution for renewable urban thermal energy supply

2019 ◽  
Vol 49 ◽  
pp. 129-136 ◽  
Author(s):  
Stef Boesten ◽  
Wilfried Ivens ◽  
Stefan C. Dekker ◽  
Herman Eijdems
Keyword(s):  
Large Scale ◽  
Fossil Fuel ◽  
Supply And Demand ◽  
District Heating ◽  
Thermal Storage ◽  
Energy System ◽  
Heat Pumps ◽  
Urban Environments ◽  
Cooling Systems ◽  
Heating And Cooling

Abstract. In order to reduce greenhouse gas emissions and decrease dependency on depleting fossil fuel resources the shift to a renewable energy system is necessary. District heating and cooling systems are a viable solution to provide heat and cold in urban environments. Renewable heat and cold sources that may get incorporated in future urban energy systems will not provide the same high temperature output as current fossil fuel fired systems. Fifth generation district heating and cooling (5GDHC) systems are decentralized, bi-directional, close to ground temperature networks that use direct exchange of warm and cold return flows and thermal storage to balance thermal demand as much as possible. 5GDHC offers a way to incorporate low temperature renewable heat sources including shallow geothermal energy, as well as reduce total demand by recuperating generated heat from cooling and generated cold from heating. The large scale of 5GDHC allows for optimal design of technical parts like heat pumps and thermal storage vessels, while increasing overall system efficiency by incorporating a large variety of supply and demand profiles. We provide a definition for 5GDHC and show how this concept differs from conventional district heating systems. The Mijnwater system in Heerlen, the Netherlands is showing what a city-level 5GDHC system can look like.

scholarly journals Local Heating Networks with Waste Heat Utilization: Low or Medium Temperature Supply?

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 954 ◽  
Author(s):  
Hanne Kauko ◽  
Daniel Rohde ◽  
Armin Hafner
Keyword(s):  
Low Temperature ◽  
Heat Pump ◽  
Urban Areas ◽  
Waste Heat ◽  
Local Heating ◽  
District Heating ◽  
Heat Pumps ◽  
Hot Water ◽  
Local Network ◽  
Medium Temperature

District heating enables an economical use of energy sources that would otherwise be wasted to cover the heating demands of buildings in urban areas. For efficient utilization of local waste heat and renewable heat sources, low distribution temperatures are of crucial importance. This study evaluates a local heating network being planned for a new building area in Trondheim, Norway, with waste heat available from a nearby ice skating rink. Two alternative supply temperature levels have been evaluated with dynamic simulations: low temperature (40 °C), with direct utilization of waste heat and decentralized domestic hot water (DHW) production using heat pumps; and medium temperature (70 °C), applying a centralized heat pump to lift the temperature of the waste heat. The local network will be connected to the primary district heating network to cover the remaining heat demand. The simulation results show that with a medium temperature supply, the peak power demand is up to three times higher than with a low temperature supply. This results from the fact that the centralized heat pump lifts the temperature for the entire network, including space and DHW heating demands. With a low temperature supply, heat pumps are applied only for DHW production, which enables a low and even electricity demand. On the other hand, with a low temperature supply, the district heating demand is high in the wintertime, in particular if the waste heat temperature is low. The choice of a suitable supply temperature level for a local heating network is hence strongly dependent on the temperature of the available waste heat, but also on the costs and emissions related to the production of district heating and electricity in the different seasons.

scholarly journals Upgrading a District Heating System by Means of the Integration of Modular Heat Pumps, Geothermal Waters, and PVs for Resilient and Sustainable Urban Energy

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2347
Author(s):  
Elżbieta Hałaj ◽  
Jarosław Kotyza ◽  
Marek Hajto ◽  
Grzegorz Pełka ◽  
Wojciech Luboń ◽  
...  
Keyword(s):  
District Heating ◽  
Heating System ◽  
Upper Jurassic ◽  
Heat Pumps ◽  
Water Levels ◽  
Energy Potential ◽  
Geothermal Waters ◽  
District Heating System ◽  
Heating And Cooling ◽  
The City

Krakow has an extensive district heating network, which is approximately 900 km long. It is the second largest city in terms of the number of inhabitants in Poland, resulting in a high demand for energy—for both heating and cooling. The district heating of the city is based on coal. The paper presents the conception of using the available renewable sources to integrate them into the city’s heating system, increasing the flexibility of the system and its decentralization. An innovative solution of the use of hybrid, modular heat pumps with power dependent on the needs of customers in a given location and combining them with geothermal waters and photovoltaics is presented. The potential of deep geothermal waters is based on two reservoirs built of carbonate rocks, namely Devonian and Upper Jurassic, which mainly consist of dolomite and limestone. The theoretical potential of water intake equal to the nominal heating capacity of a geothermal installation is estimated at 3.3 and 2.0 MW, respectively. Shallow geothermal energy potential varies within the city, reflecting the complex geological structure of the city. Apart from typical borehole heat exchangers (BHEs), the shallower water levels may represent a significant potential source for both heating and cooling by means of water heat pumps. For the heating network, it has been proposed to use modular heat pumps with hybrid sources, which will allow for the flexible development of the network in places previously unavailable or unprofitable. In the case of balancing production and demand, a photovoltaic installation can be an effective and sufficient source of electricity that will cover the annual electricity demand generated by the heat pump installation, when it is used for both heating and cooling. The alternating demand of facilities for heating and cooling energy, caused by changes in the seasons, suggests potential for using seasonal cold and heat storage.

scholarly journals A Method for Optimizing and Spatially Distributing Heating Systems by Coupling an Urban Energy Simulation Platform and an Energy System Model

Resources ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 52
Author(s):  
Annette Steingrube ◽  
Keyu Bao ◽  
Stefan Wieland ◽  
Andrés Lalama ◽  
Pithon M. Kabiro ◽  
...  
Keyword(s):  
District Heating ◽  
Energy Systems ◽  
Energy System ◽  
Heat Pumps ◽  
Energy Simulation ◽  
Heating Systems ◽  
Optimal Amount ◽  
Urban City ◽  
Urban Energy ◽  
Building Level

District heating is seen as an important concept to decarbonize heating systems and meet climate mitigation goals. However, the decision related to where central heating is most viable is dependent on many different aspects, like heating densities or current heating structures. An urban energy simulation platform based on 3D building objects can improve the accuracy of energy demand calculation on building level, but lacks a system perspective. Energy system models help to find economically optimal solutions for entire energy systems, including the optimal amount of centrally supplied heat, but do not usually provide information on building level. Coupling both methods through a novel heating grid disaggregation algorithm, we propose a framework that does three things simultaneously: optimize energy systems that can comprise all demand sectors as well as sector coupling, assess the role of centralized heating in such optimized energy systems, and determine the layouts of supplying district heating grids with a spatial resolution on the street level. The algorithm is tested on two case studies; one, an urban city quarter, and the other, a rural town. In the urban city quarter, district heating is economically feasible in all scenarios. Using heat pumps in addition to CHPs increases the optimal amount of centrally supplied heat. In the rural quarter, central heat pumps guarantee the feasibility of district heating, while standalone CHPs are more expensive than decentral heating technologies.

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.

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