Renewable Heat Research Articles

Modeling of a Solar Thermal Plant to Produce Hot Water and Steam for a Brewery Factory

The environmental impact caused by the intensive exploitation of fossil fuels to generate heat and electricity has already reached a critical level. Also, as the industrial sector is the largest energy consumer, mainly in the form of heat, it has then become compulsive to implement the use of renewable solar heat in industrial processes, such as those found in the food processing and beverages industries, which do not require high temperatures. Consequently, this study examines the viability of supplying heat as hot water at 80 °C and saturated steam at 160 °C to a medium-sized brewery factory through a hybrid solar plant composed of flat plate and parabolic trough collectors and sensible thermal energy storage. The study was conducted numerically using the meteorological conditions of a city different from that where the factory is located because it benefits from higher insolation levels. The mean annual solar fractions achieved were 49.9% for hot water production and 37.3% for steam generation, at a levelized cost of heat of 0.032 USD/kWh, which can be considered competitive if compared against the values reported in other similar solar projects. Also, the decrease in fossil fuel consumption allowed an annual reduction of 252 tons of carbon dioxide emissions.

Direct air capture with renewable heating based on the technical lime cycle

The industry and space heating demand contributes significantly to the CO2 emissions in Germany, as it is mainly supplied by the combustion of fossil fuels. In this contribution a concept is presented that not only provides heat based on renewable sources, but is also able to actively capture CO2 from the atmosphere. Thereby, the reversible reaction of lime with water is utilised to store and provide heat on demand – all based on abundantly available resources. By closing the technical lime cycle this long-term energy storage could additionally be combined with a Direct Air Capture technology.

Analysis of Different Climate-Neutral Heat Supply Concepts for a District Heating System near Munich with Deep Geothermal Heat as the Primary Heat Source

District heating systems are one key element of the transition towards a climate-neutral heat supply since they allow for the use of various renewable energy sources and the increase of renewable heat generation, in particular when combined with seasonal thermal energy storage. Deep geothermal heat is a renewable heat source that can be used to cover the thermal base load of such a district heating system. Also in combination with other renewable heat sources, such as solar thermal or heat pumps, a climate-neutral heat supply for districts or even complete cities can be realised. This paper deals with the analysis of different climate-neutral heat supply concepts that were elaborated for a district heating system currently in the planning phase using deep geothermal heat as the primary heat source, located in the town of Graefelfing near Munich, Germany. The authors present, discuss and assess various options regarding renewable heat sources and including (seasonal) thermal energy storage, to fully cover the thermal loads of a new district heating system in a technically, economically and environmentally favourable way. As a result of this study, a heat supply concept was selected, in which a heat pump using the return flow of the deep geothermal circuit as a heat source maximises the utilisation of the available deep geothermal heat source to cover more than 95 % of the annual heat demand by deep geothermal heat combined with a heat pump.

Energy Savings, Environmental Impacts and Monitoring Results of a Pumped Solar Water Heating System at Katutura Hospital Maternity Ward, Namibia

The SADC region is endowed with solar radiation between 1800-2400 kWh/m2 [1]. Nevertheless only 0.3 % of the worldwide solar thermal capacity is installed in the Sab-Saharan African Countries. Therefore, the main goal of the Southern African Solar Renewable Heating and Cooling Initiative (SOLTRAIN+) project funded by the Austrian Development Agency is to contribute to the transformation of the energy system to a sustainable, affordable and carbon-free system. This will be done by the implementation of Renewable, Heating and Cooling (RHC) systems in the targeted sectors: buildings, industry & commerce, tourism and hospitals, and enable this by a holistic capacity building. RHC technologies are solar thermal, heat pump and energy efficiency. This study therefore intends to evaluate and produce energy balance, based on real data recorded from January 2023 to December 2023 on a 120 m2 collector area with 8000 litres storage tanks, and a 22 kW heat pump, installed at Katutura State Hospital maternity ward.

Modelling physical controls on mine water heat storage systems

The use of abandoned mines as a heat source and store has been receiving increased attention as a renewable heat source and storage solution in the transition away from traditional gas heating. The hydraulic, thermal and geomechanical processes governing heat storage and extraction are complex and understanding these processes is critical to safe heat extraction and injection into mine water systems. This paper outlines the development of a fully coupled thermo-hydraulic-mechanical (THM) 2D model to understand the mechanical stability of room and pillar workings during heat injection and extraction. It was found that the cyclical injection and extraction of heat does have an impact on both the modelled displacements and mechanical stability of the system. The impact risk reduces with temperature and the operational processes (e.g. injection temperature and water level) have more of an impact than the underlying geological conditions. These results are significant and could be included in a regulatory system to reduce the likelihood of stability impacts in mine water heating and cooling schemes. Thematic collection: This article is part of The Earth as a thermal battery: future directions in subsurface thermal energy storage systems collection available at: https://www.lyellcollection.org/topic/collections/thermal-energy

Monitoring and Evaluation of Thermosyphon and PV Hot Water Systems Under the Same Operating Conditions in a Side-By-Side Experimental Setup

Renewable heating and cooling are the primary focus of the Southern African Renewable Heating and Cooling Training and Demonstration Initiative in creating capacity pertaining to this subject. This emphasis is aligned with the United Nation’s 2030 Agenda, which seeks for carbon-neutrality by the year 2030. To address thermal needs on small-scale, thermosiphons systems using evacuated tube collectors, flat-plate collectors, and photovoltaic to heat systems are frequently used. For a scale-up application of these technologies, and for accelerated achievement of carbon-neutrality, a cost-effective technology must be prioritised in various areas of the world with different meteorological conditions. This study therefore intends to establish the technical performance and the cost-effectiveness of these technologies in Namibia’s environment whilst replicating a small-scale house daily hot water demand.

Environmental Health Predictions for Fire Resistant and Corrosion Protection Measures for Community Health Tourism Building Facilities Due to Climate Change

The recent expansion of green tourism building facilities and warehouse capacities entails the installation of integrated community health tourism facility for cultural events, safe mobility, sport activities, agricultural and veterinary activities at old heritage buildings for public health, environmental health, green circular economy promotion within safe structures, which operations increase the occurrence of compartment fires involving flammable dangerous substances i.e biogas from sanitary biomass treatment for renewable resources, electricity and heating. The aim of this research is to compare and analyze the fire resistant materials of structural members and design economic solutions made of different structural materials for natural hazards and climate change. Useful results are presented for sustainable design solutions at integrated community health tourism renew facilities at old heritage buildings, applying proper utilities. Then, are examined the possibility of reinforcing the beams with carbon fiber lamellae and proposed additional fire protection requirements. The examining results present useful solutions for stakeholders. The study outputs enable warehouse designers, operators, stakeholders, investors and safety experts to ensure safe building facilities. Finally, sanitary digital drawing utilities, monitoring schemes are demonstrated for safe green designs so as to protect the examining building facilities at foundations or roof top levels from flood events and high temperatures due to climate change and extreme weather events.

Design and optimization of a geothermal absorption cooling system in a tropical climate

The electricity required for air conditioning is soaring worldwide. Absorption chillers represent an alternative to classical vapor compression systems, using heat instead of electricity. However, absorption chillers powered by renewable geothermal heat have received little attention so far. This paper introduces a system using a hot geothermal fluid (typically in the range of 80–110 °C) to produce cooling through a single-effect absorption chiller, and Domestic Hot Water (DHW) through a heat exchanger. It considers a hotel located in Martinique, a French Caribbean island. The electric consumption of every subsystem has been thoroughly estimated. The originality of this paper is twice: i) the system is modelled in TRNSYS software considering dynamic conditions, ii) the system undergoes surrogate modelling and multi-objective optimization to minimize both the cost and the CO2 content of the delivered thermal energy. Several scenarios are considered, depending upon the geothermal temperature, mass flow rate, well remoteness, and demand size. The studied system appears to be systematically more expensive than a combination of a classical vapor compression chiller and a boiler for DHW. However, it can significantly decrease the CO2 content of the provided energy, especially in an island where most electricity is generated from fossil fuels. The proximity of the geothermal well and the use of the warm water leaving the absorption generator (here for DHW production) appear to be key factors for system relevance, along with a hotter geothermal fluid (e.g., 110 °C instead of 80 °C).

Recent Research in Solar-Driven Hydrogen Production

Climate concerns require immediate actions to reduce the global average temperature increase. Renewable electricity and renewable energy-based fuels and chemicals are crucial for progressive de-fossilization. Hydrogen will be part of the solution. The main issues to be considered are the growing market for H2 and the “green” feedstock and energy that should be used to produce H2. The electrolysis of water using surplus renewable energy is considered an important development. Alternative H2 production routes should be using “green” feedstock to replace fossil fuels. We firstly investigated these alternative routes through using bio-based methanol or ethanol or ammonia from digesting agro-industrial or domestic waste. The catalytic conversion of CH4 to C and H2 was examined as a possible option for decarbonizing the natural gas grid. Secondly, water splitting by reversible redox reactions was examined, but using a renewable energy supply was deemed necessary. The application of renewable heat or power was therefore investigated, with a special focus on using concentrated solar tower (CST) technology. We finally assessed valorization data to provide a tentative view of the scale-up potential and economic aspects of the systems and determine the needs for future research and developments.

Is District Heating a cost-effective solution to decarbonise Irish buildings?

Achieving decarbonisation of the heating sector is a major challenge, especially in Ireland, which has the lowest proportion of renewable heat in Europe. In economically pursuing ambitious and equitable climate targets, Ireland’s Climate Action Plan 2023 set a goal of reaching 2.5 TWh of district heating by 2030, starting from a limited existing capacity. This pioneering study explores supply sources and heat density demand cohorts to develop a model to understand district heating in a low-deployment region, using Ireland as a case study. We also conduct a sensitivity analysis considering different connection rates.Our research demonstrates that district heating is pivotal in achieving optimal decarbonisation pathways. Incorporating district heating reduces marginal CO2 emission prices by 13%–25%. Additionally, with feasible growth limits applied, total savings for the energy system are anticipated to reach €17.2 billion by 2050. This reduction of emissions in the building sector, facilitated by district heating, allows for greater emissions allowances in other sectors and reduces reliance on electricity while meeting climate targets. These insights highlight the need for spatial energy policies and deepen our understanding of integrating district heating within an energy system optimisation model.

Adoption of renewable heating systems and thermal energy communities in the Netherlands: An empirical study

Renewable heating systems (RHS), such as solar thermal, geothermal, heat pumps, wood pellets, biomass, are essential to reduce dependence on fossil fuel-based heating systems and resulting CO2 emissions. Despite their benefits in terms of CO2 emissions, the widespread adoption of RHS has yet to be achieved. This paper aims to get insights into the intention to adopt RHS in the Netherlands For this purpose, it designs and conducts a survey based on the extended version of the theory of planned behavior, with five components: attitude, subjective norms, perceived behavioral control, personal norms, and descriptive norms. The survey also includes questions on participation in a thermal energy community. The results show that several factors affect individuals’ intention to adopt RHS. Many individuals in the Netherlands have a positive attitude toward adopting RHS, which is primarily caused by environmental concerns and wanting energy independence for their country. However, the majority of individuals think that they do not have the knowledge, financial means, or time to adopt RHS. Also, individuals who feel strong moral values and responsibilities are more likely to adopt RHS. Most individuals are willing to participate in a thermal energy community, and prefer participating in an energy community over adopting RHS individually. Based on these insights, a number of recommendations are made to stimulate the adoption of RHS in the Netherlands, such as taking into account moral norms, introducing policies to incentivize thermal energy communities, and addressing issues of injustice.

Field Trial Evaluation of a Hybrid Heat Pump in an Existing Multi-Family House before and after Renovation

Renovation of existing buildings is fundamental to reduce greenhouse gas emissions of the building sector and to ensure the efficient operation of renewable heating systems. In multi-family houses, the suitability of heat pumps is limited by high required temperatures for the hot water preparation, which can be mitigated by hybrid heat pump systems. In this study, the energetic performance of a hybrid heat pump in a multi-family house, built in 1964, is investigated based on field data before and after a renovation. Multiple months are measured and mapped to a full year period. The combination of different renovation measures in the heating system and building envelope is rated w.r.t. their ecological and economical impact by taking into account the actual investment costs. The evaluation shows that the installation of a hybrid heat pump can achieve an accumulated greenhouse gas emissions reduction of 45%, which is similar to a building renovation to a new-build standard, which reduces the space heating demand by up to 62%. Nevertheless, only a combination of both measures can substantially reduce the emissions, which in this case are 81% lower compared to a gas boiler in 1990, which is still below the German climate target for 2040. Due to the low investment costs of a hybrid heat pump system, tenants are more likely to profit from a renting costs reduction, while a building renovation is especially economically beneficial at high energy prices. The results therefore emphasize that the insulation level should be selected carefully, as heat pumps already prepare space heating efficiently and that the heat pump must be able to support the hot water preparation to reach high emission reduction targets.

Optimization of solar and heat pump complementary powered desiccant air conditioning system

The effective utilization of renewable heat sources is critical for energy saving in desiccant air conditioning systems. A new solar and heat pump complementary powered desiccant air conditioning system is proposed. The system consists of a solar and water source heat pump complementary reheat subsystem, a two-stage desiccant wheel, a three-stage air cooler, and a two-stage heat pipe exchanger. Simulation are performed in the transient simulation software TRNSYS, and the particle swarm optimization and the Hooke Jeeves algorithm with life cycle cost as the objective function are applied to optimize the collector area, the heat storage tank volume and the water-source heat pump power. The results show that the monthly average coefficient of performance of the system is 5.1, 5.6, 5.5 and 4.8 in June, July, August and September, respectively. Compared to the conventional air conditioning system, the new system has a 58.4% reduction in operation cost and a payback period of 6.6 years. The CO2 emission reduction rate of the new system can reach 65.2% in July and 65.1% in August, while it is the lowest in September at 62.9%. Based on the above, the new system has better energy efficiency, economic and environmental benefits.

Case Study on Decarbonization Strategies for LNG Export Terminals Using Heat and Power from CSP/PV Hybrid Plants

The race towards decarbonization is driving major oil and gas companies to explore means to use renewable heat and power for their plants as part of their commitment to reduce their carbon intensity by 80% to 100% by 2050 [1]. In terms of greenhouse gas (GHG) emissions, natural gas is considered the cleanest fossil fuel option available, and decarbonization of new liquefied natural gas (LNG) projects is on the radar of many LNG projects developers. In addition, LNG cargos will have to be certified in the future by accredited authorities to meet defined GHG emission levels [2].
 This research study investigates a concept of providing both heat and power from a photovoltaic (PV) and concentrated solar power (CSP) solar tower hybrid plant to meet the energy demand of LNG export terminals. Two locations have been investigated for potential future LNG projects: Karratha in Australia and Ras Laffan in Qatar. Both locations have direct normal irradiance (DNI) values higher than 2000 kWh/m2/year, which is the minimum level required for CSP technology [3]. A techno-economic assessment was carried-out taking into consideration the electricity price, the grid carbon intensity and the carbon dioxide (CO2) tax in the region.
 The results indicate that the CSP/PV hybrid plant significantly accelerates the decarbonization of energy supply to the “All electric” LNG Plant. The quantity of CO2 emitted between 2025 and 2050 is reduced by 81% for Karratha (Australia) and by 88% for Ras Laffan (Qatar) compared to a grid connected LNG plant.

Planning of renewable energy regional heating system based on demand side uncertainty

Effective planning of renewable energy district heating systems is essential to facilitate the energy transition and achieve environmental goals. In the face of demand-side uncertainty, the complexity of system planning increases significantly. To address this challenge, a new approach has been adopted to optimize heating systems by precisely analyzing and managing demand-side variables. Using simulation experiments to quantitatively assess uncertainty factors, it is found that room temperature, unit ventilation, equipment power, and lighting power had significant effects on system energy consumption, ranging from −17% to 12%. According to these factors, a series of optimization measures are formulated, and then a set of optimization scheme based on demand-side uncertainty is implemented. The experimental results show that the scheme can effectively reduce the daily power output, reduce the total cost input by 7.1%, and achieve a total emission reduction of 4.0% in environmental protection. The optimization strategy proposed in this study significantly reduces energy consumption and costs, and reduces carbon emissions, providing a new solution for the environmental protection and intelligent heating system.

Renewable process heat from solar thermal: Poultry slaughterhouse processes

Jordan faces pressing energy challenges, characterized by a substantial dependence on imported resources. This paper addresses these challenges by examining the potential integration of solar thermal energy systems into poultry slaughterhouses, using a representative case study. The study starts by providing a brief background on Jordan's energy challenges and the rationale for exploring solar thermal applications in the poultry industry. The methodology involves a meticulous analysis of existing processes in the slaughterhouse, followed by the necessary calculations for integrating a solar thermal flat plate collector. Validation is performed through T*SOL and Polysun simulations, accompanied by a comprehensive economic analysis. The proposed flat plate collector-based system demonstrates the capacity to cover approximately 72% of the facility's annual energy requirements, resulting in substantial savings of 1,926,396 kWh per year, equivalent to 330,318 L of diesel. Simulation results indicate a concise payback period of 3.8 years and net profits approximately 6.6 times the initial investment over a 25-year span. Beyond economic benefits, the adoption of solar technology leads to an 84% reduction in annual CO2 emissions, underscoring its environmental advantages. The study also sheds light on a notable lack of awareness about solar thermal technology, emphasizing the need for knowledge dissemination to foster global renewable energy adoption.

Comparison study of the renewable water source heat pump system with the conventional system

Comparison study of the renewable water source heat pump system with the conventional system

Hybrid Technologies for Water Heating Applications: A Review

The over-reliance on fossil resources necessitates the development of a sustainable energy system. Renewable energy and efficient hybrid water heating technologies are viable net-zero energy options. The economic benefits of these hybrid technologies offer a promising prospect for widespread adoption in developing countries as a means of increasing the hot water production. These hybrid technologies are becoming increasingly popular for domestic thermal applications in remote areas to compensate for energy shortages. This paper provides an overview of hybrid renewable water heating technologies with a focus on hybrid configurations, optimization techniques, mono-particle, and hybrid nanofluids and modelling. This paper also highlights the prospects for increasing the economic attractiveness and public acceptance of such systems.

Distributed energy management of multi-area integrated energy system based on multi-agent deep reinforcement learning

This paper addresses the problem of distributed energy management in multi-area integrated energy systems (MA-IES) using a multi-agent deep reinforcement learning approach. The MA-IES consists of interconnected electric and thermal networks, incorporating renewable energy sources and heat conversion systems. The objective is to optimize the operation of the system while minimizing operational costs and maximizing renewable energy utilization. We propose a distributed energy management strategy that makes hierarchical decisions on intra-area heat energy and inter-area electric energy. The strategy is based on a multi-agent deep reinforcement learning framework, where each agent represents a component or unit in the MA-IES. We formulate the problem as a Markov Decision Process and employ Q-learning with experience replay and double networks to train the agents. The proposed strategy is evaluated using a simulation of a four-area MA-IES. The results demonstrate significant improvements in energy management compared to traditional methods, with higher renewable energy utilization and lower operational costs. Specifically, the strategy achieves 100% utilization of wind power, and decreases operational costs by 5.53%. Furthermore, it leverages the generalization capabilities of reinforcement learning to respond in real-time to uncertainties in demand and wind power output. The results highlight the advantages of the proposed strategy, making it a promising solution for optimizing the operation of multi-area integrated energy systems.

Spatial analysis of renewable and excess heat potentials for climate-neutral district heating in Europe

District heating can play a decisive role in the transformation to a climate-neutral building sector, replacing fossil fuels. Renewable and excess heat potentials for district heating are often spatially limited and a consistent EU-wide analysis of the potentials is not yet available. In this paper, we quantify the renewable and excess heat potentials that could supply future district heating areas for the entire EU. We combine different data sets with a high spatial resolution and conduct spatial matching. Subsequently, we cluster the results for the potentials for individual district heating areas to derive representative types. The results show that the renewable and excess heat potentials together with heat pumps are overall sufficient to supply the future district heating demand, with high technical potentials from geothermal heat and excess heat from wastewater treatment plants. Decreasing the system temperatures increases the amount of available potentials. Lower heat densities and the overall character of the future supply sources require a paradigm shift in DH systems. Large central CHP units will need to be replaced by a diversity of several smaller sources, often combined with heat pumps and utilized at lower system temperatures.