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Industrial heat production is responsible for around 20% of total greenhouse gas emissions in Europe. To achieve the climate change goals defined in the Paris Climate Agreement, the EU commission has shifted its focus on sustainable means to generate heating. Moreover, global dependencies are leading to a re-organization of natural gas supplies. Therefore, there is a need for less vulnerable and less price-volatile solutions for heating. This paper focuses on two decarbonization technologies for industrial process heat supply: a) electricity-driven steam-generating high-temperature heat pumps (HTHP), a technology that is more efficient than fossil fuel boilers in generating steam, and b) solar parabolic trough collector (PTC), which can produce heat economically and at a minimal carbon footprint compared to other technologies. The main aim of this paper is to evaluate the levelized cost of heat (LCOH) of these technologies to fulfill a comparative techno-economic analysis. A maximum PTC collector's solar fraction limit (SFlimit) is defined to indicate when the LCOH for these two technologies is equal. This allows for distinguishing between the economic stronghold of each technology. The evaluation is carried out through the annual energy simulations using TRNSYS and Excel spreadsheets for HTHPs, while TRNSED and OCTAVE are used for the solar thermal part. Boundary conditions for European geographical constraints have been applied to establish use cases for the analysis. The result shows that the design of a PTC system with optimal SF can reach cost parity with HTHP for most of the analyzed locations. The developed methodology serves as a valuable guide to quickly determine a preferred lower carbon heat solution, thus easing the decision-making for industries.

This paper focused on the performance monitoring and modeling of a 6.0 kW, 2000 L hybrid direct expansion solar assisted heat pump (DX-SAHP) water heater used for the production of hot water in a university students’ accommodation with 123 females. The data of total electrical energy consumed, volume of hot water consumed, ambient temperature, relative humidity, and solar irradiance were obtained from the data acquisition systems and analyzed in conjunction with the energy factor (EF) of the system. A multiple linear regression model was developed to predict the EF. The EF of the hybrid DX-SAHP water heater was determined from the summation of the coefficient of performance (COP) of the heat pump unit and the solar fraction (SF) of the solar collectors. The operations of the hybrid energy system were analyzed based on three phases (first phase from 00:00–08:00, second phase from 08:30–18:30, and third phase from 19:00–23:30) over 24 h for the entire monitoring period. The average EF of the hybrid energy system per day during the second phase of operation was 4.38, while the SF and COP were 0.697 and 3.683, respectively. The developed multiple linear regression model for the hybrid DX-SAHP water heater accurately predicted the determined EF.

The utilization of a hybrid energy system (combined solar water heater (SWH) and an air source heat pump (ASHP) water heater) can result in over 80% reduction in the electrical energy consumed as the system is capable to operate with an energy factor of above 4.0. A major challenge is to develop credible methodology or mathematical model to predict energy savings. The research focused on the design and installation of a hybrid energy system and a data acquisition system to monitor its performance. The average weekday volume of hot water consumed, thermal energy gained by water in the tank of the air source heat pump (ASHP) water heater, electrical energy consumed, and the COP were 225.03 L, 5.25 kWh, 1.52 kWh, and 3.50. The average weekday global solar radiation, ambient temperature, solar fraction of the solar water heater (SWH) and the energy factor of the hybrid energy system were 579.67 W/m2, 23.58°C, 0.52, and 4.02, respectively. A multiple linear regression model was developed to predict the energy factor of the hybrid energy system. Both the modelled and validated results showed very good determination coefficients of 0.952 and 0.935, with the trained and validated dataset. Hence, by employing both multiple linear regression model and a multiple 2D contour plot simulation, the energy factor and the variation of the input parameters can be accurately determined. The developed model can help homeowners, energy service companies, and policy makers to appreciate and confidently support the rollout of the technology for sanitary water heating.

The negative impacts of the increasing number of air conditioning systems in Australia include excessive strain on grids and associated blackouts, higher electricity costs and associated carbon emission issues. The installation of sustainable cooling technologies such as solar absorption cooling systems provides a promising alternative. However, the feasibility of the system for the Australian subtropical climate has not systematically studied. The paper aims to investigate the feasibility of implementing solar absorption cooling technology in student residential building in Australia's subtropical climate region. The feasibility study allows the user to determine if the solar cooling system is technically, economically and environmentally sustainable in the long term. Through the simulation, the key performance parameters such as power consumption data and component performance details were determined. The simulation results showed that the solar absorption chiller can provide comfort in the building by maintaining room temperature within 20–24 °C. The system's performance optimisation studies were conducted, and it was found that the collector area 20 m2 paired with a storage ratio of 0.02 m3/m2 had provided a high solar fraction (SF) of 0.91. The economic analysis is also carried out to determine the annual savings in energy cost, carbon emission reduction, and the payback period.

Middle East and North Africa region's abundant solar and wind resources provide a valuable opportunity to diversify energy production and offer a high potential for renewable energies. Thus, the solar water heating systems offer a key element in the deployment of renewable energy throughout the region. To this end, a model was developed and validated to evaluate the performance of these systems with different collectors. Then, an exhaustive energetic, exergetic, environmental and economic analysis of all the region's countries was carried out on the basis of the required meteorological data. Regarding the results for the entire region, the maximum solar fraction values attain 60 % and 83 % for the flat plate and evacuated tube systems, respectively. Under current economic assumptions, propane water heating is cheaper on a life cycle cost basis than electric and diesel heating throughout North Africa. Also, the use of auxiliary electric generators is suitable for all countries in the Middle East region except for Manama-Jordan, Abu Dhabi-UAE and Ankara-Turkey.

In recent years Solar Domestic Hot Water systems have increased significantly their market share. In order to better understand the real-life performance of SDHW systems, a single detached house was selected for extensive monitoring. Two solar panels were installed on the house roof to provide thermal energy to the Domestic Hot Water (DHW) system. The house was equipped with data logging system and remotely monitored with performance data collected and analyzed over one year. The paper presents the inclusive analysis and performance evaluation of SDHW system, including DHW recirculation loop, under Canadian weather conditions for average family occupancy (two adults and two kids) with daily average DHW, draws of 246 L. Moreover, the study is carried out a significant recommendation to improve the SDHW performance, decrease the gas energy consumption and reduce greenhouse gas (GHG) emissions. The SDHW performance depends mainly on DHW flow rate, draw time and duration, city water temperature, DHW recirculation loop control strategy and system layout. The performance analysis results show that 91.5% of the collected solar energy is transferred to the DHW heating load through the solar tank. The contribution to DHW heating load is about 69.4% from natural gas and 30.6% from solar. The recirculation loop is responsible for close to 34.9%, of DHW total energy.

A conceptual design study of a grid connected solar electric power system using PV array for a 5.3MW as nominal power required is presented. A Bird model has been used to estimate hourly, daily, monthly and yearly solar radiation amounts. -f-chart is a design method was chosen to simulate the fraction of the solar energy required for the load given the PV array areas and climatic conditions. Four cities in the Middle East and North Africa representing different locations at southern mediterranean region are selected Tripoli, Alexandria, Tunisia and Gaza city. Tripoli City has the best performance for 73% of nominal Power followed by Alexandria about 66% and then Gaza around 63%, Tunisia City has lowest solar fraction about 59% according to the Monthly and annual solar fraction Data.

The paper presents the results of a simulation study, in which the connection of heat pumps and buffer storage tanks has been investigated. The simulations are carried out for a new type of a solar thermal combi system with a 32 m 2 collector field leading to a solar fraction of more than 50%. In the first stage, the most influencing installation and operation parameters have been identified and optimized for typical boundary conditions of weather/climate, hot water demand, building and space heating system. Within further simulations these boundary conditions are varied to find generalized design rules for the connection of heat pumps and storage tanks. These results are presented and discussed.

In order to apply solar energy for heating purpose, we study the performance of solar heating with phase change thermal energy storage. Tests and analysis have been carried out to obtain the useful energy and thermal efficiency of the system, the energy consumption for room heating and the solar fraction, The research results showed that the heating efficiency of the system would be 31.7% and the solar fraction would be 83.6% while the average temperature indoor was 14.9 °C and outdoor was -1.5 °C The temperature change in the heating room was bigger than that in the contrast. Compound heating systems with solar collectors and phase change materials are popular nowadays as they are meeting the design requirements of buildings with energy conservation integration.

The CO2-neutral self-supply of heat and electric energy is an important objective for new and existing buildings in the future [1] , [2] . Therefor the energy autonomous house (EAH) as a new concept for single-family buildings in central Europe is presented. It represents a further development of the solar and efficiency house concepts based on full self-sufficiency in thermal (partly provided by a fireplace) and electrical energy (100%). Two occupied houses have been built in Germany and they are under an extensive scientific monitoring with real user behavior since 2014. This contribution is focused on thermal energy balances and the differences due to different user behavior and the influence of weather conditions. The evaluated solar fraction was fsol, th ≥ 71.4% and fsol, el ≥ 91.8% for both houses in 2014. So far the 100% autonomy in electricity could not be reached due to the unusual low irradiation in Jan. and Dec. 2014 (-24% / -37% compared to long term values). Nevertheless the planned low electricity consumption of ∼ 2000 kWh/year could nearly be achieved, whereby a self-consumption rate of electric energy gains of ≥ 31.8% were assumed. Further findings of 1 ½ years of monitoring of the two EAH are presented within the paper.

The solar district heating system combined with borehole thermal energy storage (BTES) in the Drake Landing Solar Community (DLSC) has managed to provide 97% of the community's annual space heating demand with solar power. Following such exceptional results, the focus of this paper is to analyse the influence of location changes on the DLSC. A model of the community is created with TRNSYS and simulations are carried out in five different locations: Helsinki [FI], Hohhot [CN], Dublin [IE], Oviedo [ES] and Perpignan [FR]. To fulfil the specific needs of each location, adaptive measures are taken by modifying key parameters of the system's original design. Results show that insulating the houses and using lower temperature heating systems can significantly increase the system's solar fraction (SF). Despite increasing SF, the use of lower temperature heating systems in well-insulated homes may result in a decrease in the BTES's efficiency (η_BTES), which is also dependent on local ground properties. In hot climates, the BTES may be omitted due to high levels of winter solar radiation. Very high SFs are found to be possible in all studied locations (>95%), as long as appropriate modifications are made to the original design when necessary.

In Denmark solar fractions up to about 50% are seen for large scale solar district heating systems. The feasibility of higher solar fractions has been investigated in a case study. There is no direct subsidy for solar heating in Denmark, but the taxes on the alternative (fuels) affects the feasibility of solar heating for any district heating plant. The results show that solar heat can be provided at competitive costs compared to what is seen at many Danish district heating plants. The utility in the case study has not yet decided on a solar district heating system size.

This paper, the future developing prospect of application of passive house in China was provided,solar indirect system combined with fresh air ventilation system with heat recovery was used in designing to provide heat to meet fresh air load in the passive house, taking the Xining city as an example. The aperture areas of solar collector in different conditions were calculated by changing the influence factors such as the tilt angle of the collector and the solar fraction. This paper analyzed the relationship of the solar collector aperture area with the tilt angle of the collector and the solar fraction. On the basis of the analysis, it is safe to draw a conclusion that the program of using solar indirect system combined with fresh air ventilation system with heat recovery in passive house in cold region and severe cold region of China is economically feasible.

A solar assisted absorption heat pump (AHP) system was installed in Tianjin University for space heating in winter and heat water supply. The primary heat source for the AHP is supplied from parabolic trough collectors. In this paper, experimental and simulation are presented to give an overview assessment of the whole system. The performance of the solar collectors in steady and transient state was investigated, the thermal efficiency curve that characterizing the optical and heat loss of the collectors was carried out with a series of tests. For the whole system, the absorption heat pump performance during operating test was measured and presented. The simulation were performed by TRNSYS using the measured meteorological data and the estimated building load with the specific building type and structure, the daily and monthly operation showed that the solar radiation had significant impact on the ratio of useful energy provided by solar collectors, a high instantaneous solar fraction during the sunshine time while a very low average daily solar fraction was seen from the simulation results, this indicated that a thermal storage is necessary to improve the system performance and lower the auxiliary energy usage.

In recent years solar hot water systems, solar heating combisystems and solar air conditioning systems have been developed faster in China. Many demonstration projects were built and a technical supporting system including technical code, computer design software and design handbook has been formed. It is introduced that developing situation of technology for solar heating and cooling in China and energy saving effects of some demonstration projects in the paper.

This paper presents a year round energy performance monitoring results of two solar water heaters with 4 m 2 flat plate and 3 m 2 heat pipe evacuated tube collectors (ETCs)operating under the same weather conditions in Dublin, Ireland. The energy performance of the two systems was compared on daily, monthly and yearly basis. Results obtained showed that for an annual total in-plane solar insolation of 1087 kWh m −2 , a total of 1984 kWh and 2056 kWh of heat energy were collected by the 4 m 2 FPC and 3 m 2 ETC systems respectively. Over the year, a unit area of the FPC and ETC each generated 496 kWh m −2 and 681 kWh m −2 of heat respectively. For 3149.7 kWh and 3053.6 kWh of auxiliary energy supplied to the FPC and ETC systems their annual solar fractions (SFs) were 38.6% and 40.2% respectively. The annual average collector efficiencies were 46.1% and 60.7% while the system efficiencies were 37.9% and 50.3% respectively for the FPC and ETC respectively. Economic analysis showed that both solar water heating (SWH) systems are not economically viable with NPVs ranging between −€4,264 and −€652 while simple payback periods (SPPs) varied between 13 years and 48.5 years.

A solar plant for hot-water production was investigated by the dynamic simulation code (TRNSYS). A typical daily home consumption for a 4 persons family was considered. The hot-water demand temperature (53 °C) is controlled by a conventional fuel auxiliary heater and a tempering valve. A heat-exchanger is considered between collector and storage tank. The fluids circulate by pumps activated by photovoltaic panels. This simplifies plant control systems and allows for stand-alone utilization of the plant. Annual energy performance, in terms of solar fraction, was calculated for three Italian localities. The economic viability of such a plant was evaluated with the life cycle savings (LCS) method, considering three conventional fuels (Gas-Oil, LPG and Electricity). Italian Government incentives show an economic viability only in comparison with electrical energy.