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This paper investigates the energy performance and sizing criteria of 5th generation district heating and cooling (5GDHC) networks as a function of the heat distribution temperature in the building systems connected to the district network. An energy simulation model of a 5GDHC network was developed in Modelica for a case study located in Denmark. Calculations were carried out for four different building heating systems. Simulation results show that reducing the heat distribution temperatures from 70 °C to 23 °C leads to around 40% annual electric energy savings (from 10.4 kWh/m2 to 6.2 kWh/m2) for the operation of the heat pumps. Heat distribution temperatures of 23 °C cause higher water mass flow rates through the network, leading to annual electric energy consumption for the circulation pumps that are almost doubled (from 0.16 kWh/m2 to 0.3 kWh/m2) compared to the reference case at 70 °C. Furthermore, the paper discusses how the results obtained from the Danish case study can be generalized and applied to other cases using a simplified mathematical approach. It is found that about 1.5% of electric energy savings can be achieved for each temperature degree reduction in the heat distribution system.

Considering the global increase in mean air temperature and society’s demand for a comfortable indoor microclimate, cooling solutions in buildings will play an essential role in achieving global climate goals. Researchers estimate that global energy consumption will be significantly affected by the energy required for cooling. Assessment of cooling demand potential is an essential step to further analyse cooling options for buildings in certain areas. Within the framework of this study, mapping of energy consumption for cooling in the city of Riga (Latvia) is carried out. Mapping allows to assess the demand in a spatial perspective, identifying areas with a denser energy demand indicator, and, accordingly, a higher potential for implementation of district cooling and this method can be used in other countries and cities as well. Energy consumption for cooling at the building level was calculated and visualized using cadastral data and building energy certificate data. The results show that the potential energy consumption for cooling in the city of Riga can reach up to 397 GWh per year and the largest proportion of energy consumption for cooling is predicted in the category of multi – apartment buildings (up to 155 GWh per year), highlighting the need to pay particular attention how cooling demand is addressed in residential building sector. Results can be further used to evaluate the technical and economic feasibility of the district cooling implementation in parts of the city.

Sea Water Air Conditioning (SWAC) technology uses deep ocean water to cool buildings. It is a non-intermittent renewable thermal energy used directly without any transformation. It may replace other air-conditioning systems powered by electrical energy (mechanical vapor compression thermodynamic cycle) or powered by other renewable energies (solar heating and cooling systems). Despite its theoretical appeal as a solution to help achieve net-zero carbon emissions, and the existence of successful deployments, SWAC technology remains scarce worldwide mainly due to its investment cost (CAPEX). One reason for this failure to scale might be the absence of experimental data detailing energy performance of SWAC systems in real-world, commercial settings. Here is presented the performance of an existing 2.4 MW SWAC system, operated by The Brando resort on the atoll of Tetiaroa in French Polynesia. Under a tropical climate, experimental results show that the Coefficient of Performance (COP) of the SWAC system can reach 20 to 150 depending on the secondary loop length, compared with conventional vapor compression systems that peak at around 5 for the most efficient. To put this in terms of carbon emissions avoided, conventional unitary split systems running in similar hotels on neighboring islands in French Polynesia (COP around 3.5) emit some 860 Tons/year compared to the estimated 225 Tons/year emitted (approximated with the emissions factor of French Polynesia in 2019) operating the Tetiaroa SWAC.

While equation-based object-oriented modeling language Modelica can evaluate practical energy improvements for district cooling systems, few have adopted Modelica for this type of large-scale thermo-fluid system. Further, to our best knowledge, district cooling modeling studies have yet to include hydraulics in piping networks alongside plant models featuring realistic mechanical systems and controls. These are critical details to include when looking to make energy and control improvements in many physical system installations. To fill these gaps, this study released new open-source district cooling models at the Modelica Buildings Library and leveraged these models for a real-world case study at the University of Colorado Boulder. The site includes six buildings connected to a central chiller plant featuring a waterside economizer. Several energy saving strategies are pursued based on the validated model, including control setpoint optimization, equipment modification, and pump setpoint adjustments. Results indicate that a combination of the studied measures can save the campus annually 84.6 MWh of energy, 8.9% of electricity costs, 58.0 metric tons of carbon dioxide emissions, while the waterside economizer cuts down chillers’ run times by 201 days/year, reducing maintenance costs and extending chiller life.

The fourth generation of district heating is an established expression for new features and configurations. This generation's overarching goal is to develop heating concepts for smart energy systems contributing to the net-zero carbon emission society by substituting older district heating generations, originally developed for fossil fuels. The evolving technology generation has to consider the future challenges of lower heat demands, increased cooling demands, and integration of renewable and recycled thermal sources. Driven by these challenges, the district heating and cooling community is fast growing and very dynamic in its innovation. This trend can be observed in the development of cold networks for both heating and cooling. Several new systems in Europe, North America, and Asia have applied newly developed heating and cooling network configurations. It is essential to consolidate these novel technical solutions into the entire family of fourth generation at this stage of development to efficiently and effectively deploy and expand district heating and cooling solutions. This paper exemplary discusses ambiguous terms to demonstrate the shortfall of not having a broad and internationally accepted vocabulary. The conclusion gives suggestions for harmonising expressions, terms, and definitions introduced and used during the last years. An interactive vocabulary will facilitate innovation and a common language.

Air conditioning in general and cooling in particular are the biggest energy sinks among all electricity consumers. Mitigating energy needs of this sector by active or passive means is a necessity. This paper offers a comprehensive review of various cooling technologies for large scale applications and compares them in terms of economy, environmental footprint and most importantly, energy requirements. There is a main focus on the potential of using expansion cooling, which is defined in conjunction with cooling effects generated during the expansion process of a gas. The interest in such cooling technology stems from the double benefit of utilizing a large-scale compressed air energy storage (CAES) system that can also provide cooling via the expansion of air. This consequently manifests in reducing the electrical demand required for cooling applications. Such a concept is beneficial for hot climates, where most of the electrical demand is reserved for offsetting the cooling load.

Over the past decades, combined heat and power production (CHP) has proven itself to be an efficient means of meeting both heat and power demands. However, high efficiency can be achieved with CHP plants when the heat load is sufficient, while lower-priority CHP plants must deal with the excess heat associated with power generation. This excess heat can be used for district cooling with absorption chillers. Although the absorption chiller is an efficient technology for using excess heat for cooling generation, its efficiency is very sensitive to driving hot water temperature. This paper provides a detailed analysis of how cooling generation in CHP plants using absorption chillers affects power generation and primary energy consumption. This study is based on the operational parameters of the Mustamäe CHP plant (Tallinn, Estonia) and the cooling demand of the Tehnopol science and business campus and proposes a sufficient cooling production capacity based on the estimation of the campus' cooling demand. Additional cooling production opportunities to meet district cooling demand are discussed and compared in this paper in terms of primary energy savings and economic profit. The study finds that for the effective use of CHP excess heat and efficient cooling production, the use of an 0.8 MW absorption cooler and 11.6 MW heat pumps is recommended. This system would use 1.9 times less primary energy for cooling generation than local cooling. [ABSTRACT FROM AUTHOR]

With the prevalent energy crisis and climate changes, decarbonising energy sector has become the need of the hour. An environmentally friendly way is the utilisation of solar energy which mainly involves the deployment of photovoltaic (PV) and/or solar thermal technology. Unlike electricity generation, the application of photovoltaics for the district heating & cooling (DHC) is relatively new. Also, this energy route is yet to be fully explored. This paper aims to provide an overview of the photovoltaic applications in the context of DHC sector. At first, the utilisation of solar energy in the DHC sector is briefly described and then the review of the available literature is carried out. It was understood that PV integration in the district heating and/or district cooling system can take place in different topologies such as PV technology, energy storage, and system configuration (centralized/distributed). On one side, this technology options support design flexibility based on local scenarios (i.e., climatic conditions, building types, energy cost). On the other side, selecting the best configuration remains a challenging task for design and planning engineers. The research database on the studied topic needs to be enhanced, with a focus on PV’s role in district cooling (DC). It is deduced that right technical and economic boundary conditions in the chosen region is important for the accelerated photovoltaic integration. Also, lower environmental impact throughout the whole life cycle of solar PV integrated DHC system is reported. PV assisted DC systems have the potential to revolutionize cooling sector, especially in the places where daytime electricity costs are high. Based on the SWOT analysis, it is concluded that there is an enormous opportunity for PV integration in the DHC sector with the upgradations in DH networks, developing DC networks and rising adoption of HPs. This overview is expected to be beneficial to researchers, policymakers and other stakeholders of district energy sector.

The 5th Generation District Heating and Cooling (5GDHC) network has great advantages in terms of integration of low-temperature resources, bi-directional operation, decentralised energy flows, and possible energy sharing. One way to develop the idea and concept of 5GDHC is to identify potential agents, including residential buildings, office buildings, shopping malls, data centres, electrical transformers, and so on, in 5GDHC in each target context. The prospects for 5GDHC have been assessed in light of the conditions in the Baltics. The multi-criteria analysis method was used to quantify the main identified barriers and drivers behind the implementation of 5GDHC systems. It should be noted that new urban areas in the Baltic states are being actively developed with low-energy buildings, so 5GDHS can be integrated to supply heat to these areas. The highest score in the multi-criteria assessment was achieved by Lithuania due to support availability and open heating market conditions. When all applied criteria are weighted equally, Estonia has the most favourable conditions for 5GDHC systems due to widespread use of heat pumps and greater excess heat potential.

Electric Centrifugal Chillers (ECC) are mostly incorporated into District Cooling (DC) systems for charging the Thermal Energy Storage (TES) tank or/and to supply Chilled Water (CW) directly to the DC network for Air Conditioning (AC). ECC accounts for the highest percentage of the total electrical energy consumption, making it the most energy-intensive system in the DC setup. The high positive correlation between energy consumption and cost, and its influence on the decision-making process, necessitate the requirement to conduct an economic performance evaluation of the ECC plants. To achieve this objective, a Life Cycle Cost (LCC) analysis is performed to quantify the economic implication resulting from the ECC system's acquisition, operation, and maintenance. In this analysis, four (4) ECC systems installed in a large DC plant in Malaysia are considered the case study. The result obtained from the analysis of the study year revealed that April and June accounted for the maximum and minimum cost implication per outcome, respectively. It is also observed from the results that the climatic temperature conditions had a significant influence on the monthly cooling demand, energy consumed, and cost incurred. The operational phase of the system's life cycle accounted for the highest cost implication from the overall LCC result. A significant reduction in the operating cost is recorded as the indirect energy source used for driving the chiller plant is switched from the electricity supplied from the National Electricity Grid (NEG) and supplied from the Natural Gas Plant (NGP). The LCC per refrigeration ton of the ECC system is estimated to be MYR 1.44/RTh. The impact of system degradation (i.e. decrease in Coefficient of Performance (COP) value) over time on the overall cost per output refrigeration was also investigated. The study also revealed that operating an actual ECC system on electricity from NGP led to a 31% cost savings compared to an ideal system running on electricity from NEG. A sensitivity analysis is also conducted at the end of the study to determine the influence of the input variable on the output result.

In this study, the performance of different cooling technologies from energy and economic perspectives were evaluated for six different prototype residential Nearly Zero Energy Buildings (NZEBs) within a planned future city district in central Sweden. This was carried out by assessing the primary energy number and life cycle cost analysis (LCCA) for each building model and cooling technology. Projected future climate file representing the 2050s (mid-term future) was employed. Three cooling technologies (district cooling, compression chillers coupled/uncoupled with photovoltaic (PV) systems, and absorption chillers) were evaluated. Based on the results obtained from primary energy number and LCCA, compression chillers with PV systems appeared to be favorable as this technology depicted the least value for primary energy use and LCCA. Compared to compression chillers alone, the primary energy number and the life cycle cost were reduced by 13%, on average. Moreover, the district cooling system was found to be an agreeable choice for buildings with large floor areas from an economic perspective. Apart from these, absorption chillers, utilizing environmentally sustainable district heating, displayed the highest primary energy use and life cycle cost which made them the least favorable choice. However, the reoccurring operational cost from the LCCA was about 60 and 50% of the total life cycle cost for district cooling and absorption chillers, respectively, while this value corresponds to 80% for the compression chillers, showing the high net present value for this technology but sensitive to future electricity prices. [ABSTRACT FROM AUTHOR]

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The current energy security crisis is primarily a heating crisis. Space and water heating accounts for almost one-third of the EU’s final energy consumption, and unfortunately, around 62% of this demand is still met by fossil fuels. In this context, heat pumps, geothermal energy, and other renewable energy sources emerge as crucial technologies offering effective solutions to enhance energy efficiency and decrease dependence on fossil fuels as well as to achieve the EU energy and climate goals. This article focuses on the analysis of the potential and opportunities of using heat pumps and geothermal energy in conventional heating systems and district heating networks. This topic requires an in-depth analysis of the current state, challenges, benefits, and prospects of these technologies in the EU market. By examining the possibilities for wider adoption and discussing the associated factors, the article aims to provide valuable insights into and recommendations for the advancement of heat pumps and geothermal energy in the EU, along with the presentation of some case studies in this field. [ABSTRACT FROM AUTHOR]

District cooling systems offer a promising alternative to conventional cooling, thanks to overall larger efficiencies and reduced carbon footprint. On the other hand they are characterized by large capital and operational costs that impede their diffusion. Optimizing the design and operation of these systems is therefore fundamental to fully exploit their potential. This paper proposes a novel optimization framework for the simultaneous optimization of design and operation of these systems. The model integrates a genetic algorithm at a master level with Mixed Integer Linear Programming models at a lower level. This approach enables the optimization of various aspects, including network topology, plant locations, supply temperatures and the selection of thermal storage technology. The study showed that in the specific case of Singapore, where the cost for space occupancy is significant, latent heat thermal storages are preferred. In addition, the results highlighted the cost benefits of thermal storage, as district cooling networks lacking it can be from 6.2% to 20.8% more expensive, depending on the scenario. Furthermore, the study demonstrated that the utilization of waste heat through absorption chillers enhances the economic feasibility of district cooling, lowering the payback time by up to 5 years. Lastly, it was observed that 3 °C increase of the indoor set point temperature could reduce the payback time by 3 years and increase the final net present value by 43%, as larger network supply temperatures allow chillers to operate with better performances. The developed model allows to estimate various crucial outcomes with few input parameters, representing a useful tool for both research and planning. • A hierarchical optimization model has been implemented. • NPV can be increased by 43% with an increase of 3 °C of indoor set point temperature. • When waste heat is available, payback time can decrease by up to 5 years. • District cooling without thermal storage is up to 20.8% more expensive. • Electricity cost influences the network topology and storage strategy. [ABSTRACT FROM AUTHOR]

District heating and cooling systems have been present on the European market for more than a century, constantly evolving into more efficient energy infrastructures important for decarbonization of the heating and cooling sectors. With roughly 17,000 operational district heating systems, serving over 70 million citizens, currently, the final energy consumption attributed to district heating in Europe is estimated at over 450 TWh. As the European district heating and cooling sector varies extensively in every analyzed aspect, there are vast differences between European countries regarding technical preferences, technological development, market structure and regulatory frameworks of these systems. The main purpose of this paper is to provide a comprehensive overview of the present status of the district heating and cooling systems in Europe with insight(s) and suggestions into future trends. In addition, the provided data serves as a valuable baseline for future research. Finally, this paper draws attention to the new socio-demographic approach, observed when analyzing the district heating and cooling systems, that has been recently introduced into the scientific community. This new approach also reveals the opportunity for creating new indicators that will influence the modeling of existing and future district heating and cooling systems. • Provides a review on ongoing trends in European district heating and cooling sector. • Analyses European DHC systems from technological, market, and regulatory aspect. • Provides an overview on commonly used performance indicators and energy models. • Discusses the possibility of creating new DHC indicators. • Discusses the trends in future DHC development. [ABSTRACT FROM AUTHOR]

Fifth‐generation district heating and cooling (5GDHC) networks are a promising technology to decarbonize the heating and cooling supply of buildings and districts. Up to today, only a small number of 5GDHC networks have been built, mostly in Switzerland and Germany. As a result, there are substantial uncertainties and knowledge gaps in the planning and operation of 5GDHC networks. Herein, a survey is conducted among utility companies and engineering offices to collect data on 53 5GDHC systems in Germany, including technical, economic, and political key figures and design decisions. Results show that 5GDHC networks are mostly planned for small new build districts (less than 100 buildings). The most frequent heat sources are horizontal geothermal collectors (used in 23 networks) and geothermal probes (17 networks). 74% of the surveyed networks provide not only heat but also cold. Typical network temperatures are in the range of −5–20 °C. The survey results show that the price models as well as political design decisions, such as the obligation to connect to the network, vary strongly among the districts. [ABSTRACT FROM AUTHOR]

Electric Centrifugal Chillers (ECC) are mostly incorporated into District Cooling (DC) systems for charging the Thermal Energy Storage (TES) tank or/and to supply Chilled Water (CW) directly to the DC network for Air Conditioning (AC). ECC accounts for the highest percentage of the total electrical energy consumption, making it the most energy-intensive system in the DC setup. The high positive correlation between energy consumption and cost, and its influence on the decision-making process, necessitate the requirement to conduct an economic performance evaluation of the ECC plants. To achieve this objective, a Life Cycle Cost (LCC) analysis is performed to quantify the economic implication resulting from the ECC system's acquisition, operation, and maintenance. In this analysis, four (4) ECC systems installed in a large DC plant in Malaysia are considered the case study. The result obtained from the analysis of the study year revealed that April and June accounted for the maximum and minimum cost implication per outcome, respectively. It is also observed from the results that the climatic temperature conditions had a significant influence on the monthly cooling demand, energy consumed, and cost incurred. The operational phase of the system's life cycle accounted for the highest cost implication from the overall LCC result. A significant reduction in the operating cost is recorded as the indirect energy source used for driving the chiller plant is switched from the electricity supplied from the National Electricity Grid (NEG) and supplied from the Natural Gas Plant (NGP). The LCC per refrigeration ton of the ECC system is estimated to be MYR 1.44/RTh. The impact of system degradation (i.e. decrease in Coefficient of Performance (COP) value) over time on the overall cost per output refrigeration was also investigated. The study also revealed that operating an actual ECC system on electricity from NGP led to a 31% cost savings compared to an ideal system running on electricity from NEG. A sensitivity analysis is also conducted at the end of the study to determine the influence of the input variable on the output result. [ABSTRACT FROM AUTHOR]

Increase in energy demand is shaping both developed and developing countries globally. As a result, the endeavour to reduce carbon emissions also encompasses electrical energy storage systems to ensure environmentally friendly power production and distribution. Currently, the scientific community is actively exploring and developing new storage technologies for this purpose. The focus of this work is to compare the eco-friendliness of a relatively novel technology such as liquid air energy storage (LAES) with an established storage solution such as Li-Ion battery (Li-ion). The comparison is carried out through Life Cycle Assessment (LCA) methodology which aims to assess the environmental impacts from each life stage, according to different impact categories. In particular, the study refers to the unitary storage and the delivery of electricity as well as cooling energy, considering all the inefficiencies and limits of each technology. The results show that in the full electric case study Li-ion battery environmentally outperform LAES due to (1) the higher round trip efficiency and (2) the significantly high environmental impact of the diathermic oil utilized by LAES, accounting for 92 % of the manufacture and disposal phase. Conversely, the cogeneration case study highlights that the "flexibility" and "dualism" of LAES, capable to efficiently deliver both electricity and cooling, offset the impact related to the higher electricity consumption during the use phase. Notably in energy mix frameworks with high share of primary energy source from fossil fuels, cogenerative LAES demonstrates superior environmental performance compared to Li-ion battery (i.e. 1302 kg CO2eq /MWh e vs 1140 kg CO2eq /MWh e for Singapore energy mix), attributable to its reduced electricity consumption., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

District heating and cooling systems play an important role in future energy infrastructure by accessing local energy potentials, reducing temperature levels and exploiting synergies between energy systems. Therefore, a transition to next generation heating and cooling networks is needed, which can be realized by multi-level design, bidirectional usage of production and consumption or combined heating and cooling systems. This will increase the complexity of network design which may be hard to analyze and assess without the support of a system simulation. The following paper presents the dhcSim Modelica library which can be used to model complex district heating and cooling networks within a multi-level network structure. The library was developed as extension to the Modelica Buildings library and Modelica Standard library and provides a clear and easy to use model structure. This structure distinguishes between two-, four and multi-port-models which allows the modeling of highly complex multi-level DHC systems. The library provides models for both district heating and cooling and can be easily adapted to individual user cases. To illustrate the implementation of the library and how it can be used, a case study of a three-level district heating network is presented. Using the network simulation of the introduced example, it could be shown that the supply temperature requirements of some consumers could not be achieved by the proposed network and thus further action is needed.

District cooling (DC) can play an important role in smart energy systems. With the global trend of reducing heat loss in buildings, cooling demand will continue to increase. Considering the potential for free cooling and waste heat utilisation in DC systems, a practical approach is needed to develop new DC networks. Tallinn has over 60 years of experience in developing district heating (DH) networks. The city has installed large capacities of biomass-based combined heat and power plants (CHPs). National support mechanisms allow the DH operator to generate power from CHPs and reject heat during warmer months when the heat load is insufficient. This heat can be used for DC. This study investigates an applied approach to DC development in Tallinn’s Ülemiste City. Ülemiste City is a business park with an existing developed area of 160 000 m 2 . The main source of cooling for the DC network is an absorption chiller that uses rejected heat from a CHP 7 kilometres away from the DC plant. The current DH supply temperature in Tallinn during the non-heating season is 70 °C. To determine the optimal technical solution for an effective energy efficiency ratio of the absorption chiller and heat transmission in the DH network, various scenarios were evaluated where the DH supply temperature was 70 °C, 80 °C, and 90 °C. An assessment of the technical parameters is provided for these scenarios. The paper presents an overview of the efficient use of rejected heat from CHPs in DC.

Over the past decades, combined heat and power production (CHP) has proven itself to be an efficient means of meeting both heat and power demands. However, high efficiency can be achieved with CHP plants when the heat load is sufficient, while lower-priority CHP plants must deal with the excess heat associated with power generation. This excess heat can be used for district cooling with absorption chillers. Although the absorption chiller is an efficient technology for using excess heat for cooling generation, its efficiency is very sensitive to driving hot water temperature. This paper provides a detailed analysis of how cooling generation in CHP plants using absorption chillers affects power generation and primary energy consumption. This study is based on the operational parameters of the Mustamäe CHP plant (Tallinn, Estonia) and the cooling demand of the Tehnopol science and business campus and proposes a sufficient cooling production capacity based on the estimation of the campus’ cooling demand. Additional cooling production opportunities to meet district cooling demand are discussed and compared in this paper in terms of primary energy savings and economic profit. The study finds that for the effective use of CHP excess heat and efficient cooling production, the use of an 0.8 MW absorption cooler and 11.6 MW heat pumps is recommended. This system would use 1.9 times less primary energy for cooling generation than local cooling.

In this study, the performance of different cooling technologies from energy and economic perspectives were evaluated for six different prototype residential Nearly Zero Energy Buildings (NZEBs) within a planned future city district in central Sweden. This was carried out by assessing the primary energy number and life cycle cost analysis (LCCA) for each building model and cooling technology. Projected future climate file representing the 2050s (mid-term future) was employed. Three cooling technologies (district cooling, compression chillers coupled/uncoupled with photovoltaic (PV) systems, and absorption chillers) were evaluated. Based on the results obtained from primary energy number and LCCA, compression chillers with PV systems appeared to be favorable as this technology depicted the least value for primary energy use and LCCA. Compared to compression chillers alone, the primary energy number and the life cycle cost were reduced by 13%, on average. Moreover, the district cooling system was found to be an agreeable choice for buildings with large floor areas from an economic perspective. Apart from these, absorption chillers, utilizing environmentally sustainable district heating, displayed the highest primary energy use and life cycle cost which made them the least favorable choice. However, the reoccurring operational cost from the LCCA was about 60 and 50% of the total life cycle cost for district cooling and absorption chillers, respectively, while this value corresponds to 80% for the compression chillers, showing the high net present value for this technology but sensitive to future electricity prices.

This 34th volume of the International Journal of Sustainable Energy Planning and Management includes papers from the 2021 conference on Sustainable Development of Energy, Water and Environmental Systems (SDEWES) held October 10-15, 2021, in Dubrovnik, Croatia as well as the 7th International Conference on Smart Energy Systems held September 21-22 in Copenhagen, Denmark and two normal papers. A focus area of this issue is district heating and district cooling systems, with articles addressing resources for district heating and cooling systems, impacts of having individual district heating metres for consumers and approaches to analysing district heating systems. Another focus area is stakeholder involvement where two groups of researchers focus on stakeholders from an energy island perspective as well as from a positive energy district perspective. Both groups note the importance of factoring in stakeholders when devising transition plans. Plans for increasing the penetration of renewable energy sources for the Estonian, Latvia and Lithuanian systems are analysed using the Backbone model, finding modest increases in system costs. Lastly, an article sets up an indicator system for assessing environmental performance of European Union member states ranking, e.g., Estonian, Latvia and Lithuanian as moderate (Estonia and Latvia) to weak (Lithuania) in terms of sustainable energy performance score, based on 2019 data. [ABSTRACT FROM AUTHOR]

The planning procedure for district cooling as an urban system was described and implemented using the example of the city centre of Tallinn. The following steps were described in detail: determining cooling demand, planning cold supply and analysing cold water distribution. Based on the three proposed methods (average specific cooling load, satellite imagery analysis of a specific building, dry cooler fan counting, and the combination method), the cooling capacity of the evaluated district was estimated at 63.2 MW. In terms of cold supply, the analysis showed that free cooling with seawater can cover up to 55% of the annual cooling demand. Electric chillers and absorption chillers that use excess heat can cover the rest of the district’s cooling demand. The district cooling network was designed for three scenarios: single generating unit, two generating units and a looped network. Despite the fact that the looped network is the most expensive option, it is deemed feasible as it simplifies the connection of new consumers. [ABSTRACT FROM AUTHOR]

The scope of this investigation is to analyze recent advances in district cooling (DC) in Europe (European Union plus the United Kingdom (EU27+UK)). The study focuses on data and information from the past decade and draws a picture for the year 2016. To date, in contrast to the European district heating market, the European DC branch has barely been explored in scientific literature. In the current paper, the data that describe the actual DC market in the EU27+UK—which includes the quantity of DC plants, equivalent full-load hours, and installed capacities as well as the values for seasonal energy efficiency—are collected and then explored using a bottom-up approach. The results indicate that DC is responsible for a minor part of the useful energy demand of Europe for cooling with around 3 TWh/y. Overall, the share of the useful energy demand for DC corresponds with 1 to 2% of the EU27+UK useful energy demand. Moreover, it is worth mentioning that the penetration of DC varies considerably from country to country, and eight European Member States appear to not have district cooling systems at all. Lastly, it is observed that DC has been slowly but constantly growing in Europe for decades and is characterized by a high growth potential, particularly in the service sector. [ABSTRACT FROM AUTHOR]

The integration of district heating (DH) and cooling (DC) in the sustainable energy system of the future requires a significant reduction in operating temperatures. Supply temperatures below 70 °C are required for new 4th Generation DH. Main benefits are the use of low exergy heat sources and the reduction of heat losses. The reduction of heat losses is achieved by reducing the driving temperature difference between the medium pipe and the ground. The decrease of the return temperature level is limited by the consumer behaviour and the ground temperature level. As a consequence, the reduction of the supply temperature is accompanied by a reduction of the maximum transmittable heat flow. For energy efficiency and economic reasons, the relative heat losses are therefore an important design value for DH networks. The study proposes an approach to estimate the relative heat losses by using steady-state heat loss models and analyses the values for different DH generations. In particular, due to the rising of the near-surface soil temperature, the relative cold losses are also studied.

Targets set by the European Green Deal to increase efficiency, reach towards sustainable development and to reduce greenhouse gas emissions have placed additional focus on necessary improvements in heating and cooling sector. This article aims to determine whether the objectives set at the EU and on the member state level for achieving climate and environmental goals are being implemented at the regional and local levels. The case of Latvia is considered. A keyword extraction text analysis method is used to identify whether improving the efficiency of heating and cooling is included in regional and local sustainable development strategies. Results are evaluated by using multi-criteria analysis methods TOPSIS and AHP, to determine how much attention in the strategies is paid to direct heating and cooling supply aspects and overall efficiency aspects. Results obtained while assessing the sustainable development strategies of cities and municipalities are compared with the climate index of their heating supply. Considerable differences can be seen in the inclusion of heating and cooling efficiency improvement plans in the strategies at regional and local levels.

This 34th volume of the International Journal of Sustainable Energy Planning and Management includes papers from the 2021 conference on Sustainable Development of Energy, Water and Environmental Systems (SDEWES) held October 10-15, 2021, in Dubrovnik, Croatia as well as the 7th International Conference on Smart Energy Systems held September 21-22 in Copenhagen, Denmark and two normal papers. A focus area of this issue is district heating and district cooling systems, with articles addressing resources for district heating and cooling systems, impacts of having individual district heating metres for consumers and approaches to analysing district heating systems. Another focus area is stakeholder involvement where two groups of researchers focus on stakeholders from an energy island perspective as well as from a positive energy district perspective. Both groups note the importance of factoring in stakeholders when devising transition plans. Plans for increasing the penetration of renewable energy sources for the Estonian, Latvia and Lithuanian systems are analysed using the Backbone model, finding modest increases in system costs. Lastly, an article sets up an indicator system for assessing environmental performance of European Union member states ranking, e.g., Estonian, Latvia and Lithuanian as moderate (Estonia and Latvia) to weak (Lithuania) in terms of sustainable energy performance score, based on 2019 data.

The planning procedure for district cooling as an urban system was presented and carried out using the example of the Tallinn city centre. The following steps were described in detail: cooling demand determination, cooling generation planning and cooling transition analysis. Based on the three proposed methods (average specific cooling load, satellite imagery analysis of a specific building, counting the number of fans in dry coolers and the combination method), the cooling capacity of the evaluated district was estimated at 63.2 MW. In terms of cooling generation, the analysis shows that seawater for free cooling can cover up to 55% of the annual cooling consumption. Electric chillers and absorption chillers that use surplus heat can cover the rest of the district cooling demand. The district cooling network was designed for three scenarios: with one generating unit, with two generating units and a looped network. Despite the fact that the looped network is the most expensive option, this type of solution is considered feasible as it will make it easier to connect new consumers.

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.

[Introduction] The energy consumption of air conditioners is gradually increasing, which is one of the main reasons for the difference between the peak and valley power consumption of the power grid. Analyzing the characteristics of district cooling and cold storage technology and actively adjusting the distribution of electricity consumption of air conditioning and refrigeration systems to reduce the peak load of electricity consumption, provide references for planning, design, and operation of district cooling. [Method] Combining the literature review of cold storage engineering research and actual case analysis, we botained the characteristics of water storage and ice storage technology outside the coil, the nature of resources for district cooling and the principles to be followed. [Result] The results show that development of district cooling and cold storage technologies in China is promising. The water storage system is flexible and convenient, and it is advisable to use the electricity price mechanism to encourage users to invest themselves. As for the ice storage system outside the coil, the initial investment and total life cycle cost per unit of the cold storage system show a downward trend with the increase of the size of the cold storage system, but the change trend is gradually flattening. District cooling projects should be planned in advance. And it is regarded as a project that maximizes the benefit of resources of all members of the district. All members must participate to get the maximum benefit and share it with all members. [Conclusion] This work provides some guidance for further study on district cooling and cool storage technology.

The work examines the current issues of development, management and optimization of integrated systems in the world and in Russia. The developed algorithm for evaluating the systemic effects of an integrated heating and cooling system in the conditions of the North is described. A qualitative and quantitative assessment of socio-economic, operational, and environmental effects is obtained using the example of the city of Yakutsk. The work carried out a technical and economic calculation, technical parameters of the energy system operation and volumes of CO2 emissions reduction. The use of waste heat by absorption chillers in the production of cold can reduce electricity costs by up to 29% per month of total consumption and save up to 519 million rubles per year. The implementation of the integrated heating and cooling system technology can reduce CO2 emissions by up to 58 tons.

The pipeline networks design approach for integrated heat and cold supply systems based on absorption chillers has been developed. Within the framework of the approach, following tasks are solved: modeling consumers demand for cooling; hydraulic calculations of district cooling pipeline systems; technical and economic calculations to choose the optimal layout of pipeline systems; heat supply and cold supply systems repair and commissioning works compatibility assessment, and modeling of thermal interaction between permafrost massif and cold supply pipeline. The study of integrated heat and cold supply systems was carried out on the example of a Yakutsk city quarter using the developed approach to determine optimal variant of the system. The simulation results showed that district cooling pipelines can be laid underground with the implementation of measures to ensure preservation of permafrost soil temperature regime.

Solar thermal energy-driven double effect absorption refrigeration system (DE-ARS) for district cooling in smart cities is an efficient, and sustainable alternative for centralized air conditioning and concurrently harnesses low-grade solar energy. This work investigates ionic liquid based H2O-[mmim][DMP] mixture as an alternative working fluid to overcome the drawback of H2O–LiBr driven DE-ARS. The thermodynamic properties of H2O-[mmim][DMP] mixture is evaluated using the excess Gibbs free energy model. Performance modeling and simulation of DE-ARS is based on both energy and exergy analysis by applying the first and second laws of thermodynamic. The performance, and solution circulation ratio of parallel flow DE-ARS is assessed and optimized under various temperatures and solution distribution ratios. In comparison to the conventional H2O–LiBr, the proposed H2O-[mmim][DMP] working fluid achieves 5.22% and 4.95% improvement in COP and ECOP, respectively at Th/Te/Ta/Tc of 140/5/30/30°C . An optimization of generator temperature to achieve maximum COP and ECOP is performed for a wide range of evaporation temperature from 5 to 20°C and Ta/Tc from 30 to 40°C. An optimization of H2O-[mmim][DMP] mixture driven DE-ARS reveals the uppermost COPmax and ECOPmax of 1.81 and 0.69 for Te of 20°C and TaTc=30°C.

The rapid increase in cooling demand for air-conditioning worldwide brings the need for more efficient cooling solutions based on renewable energy. Seawater air-conditioning (SWAC) can provide base-load cooling services in coastal areas utilizing deep cold seawater. This technology is suggested for inter-tropical regions where demand for cooling is high throughout the year, and it has been implemented in islands with short distances from the coast and the deep sea. This paper proposes adjustments to the conventional design of SWAC plants to reduce implementation risks and costs. The approach is named high velocity SWAC and consists of increasing the excavation depth of the seawater pump station up to 20 m below the sea level, compared to 2 to 5 m in conventional SWAC projects. This allows a twofold increase in the speed of inlet pipeline seawater and cooling load of the plant. The cooling load can be expanded twofold with only 55% capital cost and 83% project costs, compared with the costs of a new system. In addition, this article shows that high velocity SWAC plants with thermal energy storage will have an important role supporting the dissemination of intermittent renewable sources of energy in regions where SWAC is a viable cooling alternative. [ABSTRACT FROM AUTHOR]

In this study, a novel Ocean Thermal Energy Conversion (OTEC) based tri-generation system that produces ammonia, cooling and power is developed and analysed. This OTEC plant operates on the naturally existing temperature difference that exists in various depths of the ocean. The OTEC plant used in this study is operated using a single-stage ammonia Rankine cycle. The discharge seawater from the condenser in the organic Rankine cycle is used to provide district cooling. Two different operation cases of the analysed system are considered, where for the first case 50% of the power produced is stored in the form of ammonia during the off-peak hours. The second case is for complete power production proposed for peak hours. For the case where 50% of the power produced (case 1) is used to produce ammonia the highest energy and exergy efficiency is found to be 1.37% and 56.17% respectively. As for the case where, only power is produced (case 2) the maximum energy and exergy efficiency of the OTEC plant is found to be 1.83% and 78.02% respectively. The corresponding maximum power production was 6612 kW and 13,224 kW for cases 1 and 2. The maximum hydrogen and ammonia production rate is found to be 94.35 kg/h and 534.7 kg/h at peak efficiency values. The cooling duty at the peak energy and exergy efficiency is found to be 64.4 MW where the condenser temperature is 11.38 °C. • A comprehensive study for the cooling duty associated with OTEC is performed. • Energy and exergy efficiencies of the system are found to be 1.37% and 56.17% (Case 1). • Energy and exergy efficiencies of the system are found to be 1.83% and 78.02% (Case 2). • The maximum hydrogen and ammonia production rates are 94.35 kg/h and 534.7 kg/h. [ABSTRACT FROM AUTHOR]

Climate change intensifies stress on global potable water supply. Over 2 billion people still lack access to safe potable water, hindering social and economic development in arid regions. As a result, cost-effective desalination is important. The two main desalination technologies are thermal-based and membrane processes. The membrane-based desalination process Reverse Osmosis is gaining more and more popularity. The reason is that thermal-based processes often rely on non-renewable heat sources, while high temperature heat pumps offer a sustainable alternative for heat supply. Thus, this study investigates the integration of a transcritical CO2 heat pump into thermal-based desalination processes. The CO2 process operates at up to 180 °C, with an eco-friendly working fluid. The heat pump provides both potable water and potentially cooling energy. Six configurations were considered, showing comparable energy demands to RO. Moreover, considering cooling duty, the integrated system outperforms RO. A commercially available 19 MW el transcritical CO 2 -based heat pump system can produce up to 64.000 m3/d of potable water and 75 MW of cooling energy. This highlights the potential of heat pumps as sustainable solutions for addressing water scarcity and providing cooling. [Display omitted] • Hybrid thermal desalination run by CO 2 heat pumps need the same electrical energy as Reverse Osmosis (i.e., 9.6 kWh/m3). • Electrical energy demand of water desalination is reduced to 3.2 kWh/m3 if additional value is associated with cooling energy • Commercially available heat pump power class allows up to 64.000 m3/d of potable water and 75 MW of cooling capacity. [ABSTRACT FROM AUTHOR]

In this study we provide a general review of research into district cooling. District cooling systems and services (DCS) are increasingly widely deployed and there is an associated increase in the rate of scientific production (research papers published) on the subject. In this paper, to facilitate discussion around the key parameters and issues which matter to the successful deployment of DCS, we objectively identify the central topics and themes of DCS research. To do see we employ a combination of bibliometric summary analysis, complemented by formal topic classification using a bespoke structural topic model, to inform a comprehensive literature review and summary. In doing so we verify the structure of existing research, and the spread of system design and engineering considerations that have been prominent in research to date. Moreover we are able to confirm some absences within the literature. With this, our study provides both a valuable overview of the early research into DCS, and also highlights potential research priorities for researchers planning to work on the topic. • District cooling systems (DCS) are widely used with a growing quantity of research. • In this paper, we objectively identify the central topics and themes of DCS research. • We use bibliometrics and topic classification using a structural topic model. • We present the structure of existing research, and absences within the literature. • We unveil potential research priorities for researchers planning to work on the topic. [ABSTRACT FROM AUTHOR]

The utilization of air conditioning in public and private buildings is continuously increasing globally and is one of the major factors fueling the growth of the global electricity demand. The higher utilization of renewable energy sources and the transition of the electricity-generating industry to renewable energy sources requires significant energy storage in order to avoid supply–demand mismatches. This storage-regeneration process entails dissipation, which leads to higher energy generation loads. Both the energy generation and the required storage may be reduced using thermal energy storage to provide domestic comfort in buildings. The development and utilization of thermal storage, achieved by chilled water, in a community of two thousand buildings located in the North Texas region are proven to have profound and beneficial effects on the necessary infrastructure to make this community independent of the grid and self-sufficient with renewable energy. The simulations show that both the necessary photovoltaics rating and the capacity of the electric energy storage system are significantly reduced when thermal storage with a chilled water system is used during the air conditioning season.