M2 Of Solar Collectors Research Articles

Seasonal storage for space heating using solar DHW surplus

Due to the seasonality of solar energy, achieving 100 % of annual solar fraction for domestic hot water (DHW) production is only possible by greatly oversizing the collector area of a solar system, thus creating a significant energy surplus in summer. This simulation study investigates the possibility of using this surplus to promote space heating during winter, in a moderate South European climate, to try achieving a total solar fraction of 100 %. Priority is given to the DHW reservoir, diverting the excess heat to an additional large-capacity seasonal thermal energy storage (STES) reservoir. The best configuration for the number of collectors and STES tank volume was assessed through a parametric study, to reach a compromise between a high solar fraction and a reasonable system efficiency. The results showed that a system with 10 m2 of solar collectors and a 30 m3 STES tank or, alternatively, 20 m2 of collectors and a 20 m3 tank achieved the desired solar fraction and efficiency for the chosen building and local climate conditions. A comparison with the literature shows that this strategy can achieve better results, requiring less collector area and storage volume.

Assessment of the Trilateral Flash Cycle potential for efficient solar energy conversion in Europe

The potential of the Trilateral Flash Cycle (TFC) for the efficient conversion of solar energy to power in Europe is assessed in this work. A numerical analysis of a Solar-TFC thermal power unit is performed, by applying an in-house numerical model. Flat Plate Collectors (FPC) and Evacuated Tube Collectors (ETC) are modeled as solar heat sources. Particular focus is on the technological bottleneck of the TFC, i.e. two-phase expansion, by applying a novel two-phase expansion numerical model. Annual simulations are performed with the total efficiency of the Solar-TFC maximized at each time step. The annual total efficiency of the Solar-TFC, exergy efficiency, and thermal efficiency of the TFC can be as high as 5%, 5.3%, and 11%, respectively. ETCs increase the economic viability of the Solar-TFC, particularly as the annual electricity output increases. The Levelized Cost of Electricity (LCOE) of the modeled unit is estimated in the range of 0.25 and 0.75 €/kWh, which can be further reduced by increasing the collectors’ area. The Solar-TFC unit can reduce, on an annual basis, the CO2 emissions by 2.5–47 kg per m2 of solar collectors, with the carbon footprint reduction depending on the collectors’ efficiency and the installation location.

Application of a Costing Methodology to Estimate Capital Costs of Solar Thermal Systems in Residential Portuguese Context

The concerns regarding the environmental damage require changes not only on how the energy is consumed but also how it is produced. The close relationship between energy use and the economic growth exposes the need for continuous monitoring of energy consumption, which cannot be achieved without assessing capital and operational costs from its conversion to end-use. Solar thermal systems offer few advantages over other renewable resources to meet the energy demand in the small-scale building sector. Solar-thermal technologies can play a leading role in meeting the decarbonisation targets set in Europe. The reports from the International Energy Agency (IEA) shows that solar heating has the potential to cover more than 16% of the low-temperature heat use in energy mix scenario. In Europe, this share might translate into 45% growth of the installed solar thermal capacity by 2020, setting a challenging target of 1 m2 of collector area installed per capita by 2020 and of 1.3 m2 by 2050. The main objective of the present work is to define a costing methodology able to estimate the capital cost of solar-thermal systems according to the system size and energy requirements of a specific residential building. The costing methodology consists of the derivation of a cost expression for each component by integrating thermodynamic and cost coefficients, adjusted for this kind of technology, and also taking into account real market data. The model was validated for a reference dwelling in Lisbon, with an occupation of 4 people with an estimated energy need of 2 037 kWh/year in terms of DHW. Results of the reference scenario show that is required at least 4 m2 of solar collector and the system cost ranges from 703.2€ per m2 to 763.2€ per m2, depending on the acceptable storage tank capacity.

Dynamic Modeling and Preliminary Performance Analysis of a New Solar Thermal Reverse Osmosis Desalination Process

Reverse osmosis (RO) is a desalination technique that is commonly preferred because of its low energy consumption. In this paper, an innovative, thermally powered RO desalination process is presented. This new thermo-hydraulic process uses solar thermal energy in order to realize the pressurization of the saltwater beyond its osmotic pressure to allow its desalination. This pressurization is enabled thanks to a piston or a membrane set in motion in a reservoir by a working fluid that follows a thermodynamic cycle similar to an Organic Rankine Cycle. In this cycle, the evaporator is heated by low-grade heat, such as the one delivered by flat-plate solar collectors, while the condenser is cooled by the saltwater to be treated. Such an installation, designed for small-scale (1 to 10 m3·day−1) brackish water desalination, should enable an average daily production of 500 L of drinkable water per m² of solar collectors with a specific thermal energy consumption of about 6 kWhth·m−3. A dynamic modeling of the whole process has been developed in order to study its dynamic cyclic operating behavior under variable solar thermal power, to optimize its design, and to maximize its performances. This paper presents the preliminary performance results of such a solar-driven desalination process.

Temperatures limitation of adsorptive solar powered ice maker using AC35-methanol pair

A numerical evaluation of temperatures limits of solar adsorption refrigeration machine cycle using the AC35-methanol pair is presented in this paper. The cold production was better for lower adsorption temperatures and higher temperatures of evaporating and generating. For each 1 kg of adsorbent, 1 kg of ice can be produced for temperatures of generating from 40°C to 100°C according to solar irradiance and ambient temperature. The considered lower adsorption temperature is 10°C, which can allow to produce 9 kg of ice for higher temperatures of generating up to 130°C, this needs 680 kJ of solar irradiance for surface area of 1 m2 of solar collector. The considered higher evaporating temperature is 10°C, which can allow to produce 3.5 kg of ice for higher temperatures of generating up to 144°C, this needs 622 kJ of solar irradiance for surface area of 1 m2 of solar collector.

Energetic and Financial Optimization of Solar Heat Industry Process with Parabolic Trough Collectors

The objective of this work is the investigation of a solar heat industry process with parabolic trough solar collectors. The analysis is conducted for the climate conditions of Athens (Greece) and for five load temperature levels (100 °C, 150 °C, 200 °C, 250 °C, and 300 °C). The examined configuration combines parabolic trough solar collectors coupled to a storage tank and an auxiliary heat source for covering the thermal need of 100 kW. The solar thermal system was optimized using the collecting area and the storage tank volume as the optimization variables. There are three different optimization procedures, using different criteria in every case. More specifically, the solar coverage maximization, the net present value maximization, and the payback period minimization are the goals of the three different optimization procedures. Generally, it is found that the payback period is between five and six years, the net present value is between 500–600 k€, and the solar coverage is close to 60%. For the case of the 200 °C temperature level, the optimum design using the net present value criterion indicates 840 m2 of solar collectors coupled to a storage tank of 15.3 m3. The optimization using the solar cover indicates the use of 980 m2 of solar collectors with a tank of 28 m3, while the payback period minimization is found for a 560 m2 collecting area and an 8-m3 storage tank volume. The results of this work can be used for the proper design of solar heat industry process systems with parabolic trough collectors.

Design and functionality of a segmented heat-storage prototype utilizing stable supercooling of sodium acetate trihydrate in a solar heating system

A solar heating system with 22.4 m2 of solar collectors, a heat storage prototype consisting of four 200 kg phase-change material (PCM) storage units, and a 735 L water tank was designed to improve solar heat supply in single-family houses. The PCM storage utilized stable supercooling of sodium acetate trihydrate composites to conserve the latent heat of fusion for long-term heat storage. A control strategy directed heat from a solar collector array to either the PCM storage or a water buffer storage. Several PCM units had to be charged in parallel when the solar collector output peaked at 16 kW. A single unit was charged with 27.4 kWh of heat within four hours on a sunny day, and the PCM temperature increased from 20 °C to 80 °C. The sensible heat from a single PCM unit was transferred to the water tank starting with about 32 kW of thermal power after it had fully melted at 80 °C. A mechanical seed crystal injection device was used to initialize the crystallisation of the sodium acetate trihydrate after it had supercooled to room temperature. The unit discharge during solidification peaked at 8 kW. Reliable supercooling was achieved in three of the four units. About 80% of latent heat of fusion was transferred from PCM units after solidification of supercooled sodium acetate trihydrate to the water tank within 5 h. Functionality tests with practical operation conditions on the novel, modular heat-storage configuration showed its applicability for domestic hot water supply and space heating.

Exergo-Economic Evaluation of the Cost for Solar Thermal Depuration of Water

A detailed assessment of the cumulative cost of clean water production by a natural circulation solar thermal system is presented. The system is designed and sized for sufficient residence time for pasteurisation, in a buoyancy-driven self-compensating circuit. Since it does not consume electricity, it is suitable for developing countries or emergency locations with safe drinking water issues. The principles for design and off-design simulations are explained and discussed. The simulations were performed for seven different locations, representing variable climate conditions in selected regions where there is an evident need for safe water. The results include an exergy and exergo-economic analysis. The production capacity reaches typically from 0.04 to 0.1 m3/day per m2 of solar collector depending on the location. The annual cost of water production ranges between 2.2 and 6.8 €/m3 making the proposed system fairly competitive; the energy- and price-performance of the system is compared to a reverse osmosis/photovoltaic system, representing a high-tech alternative for the purpose of water purification.

Advantages of variable driving temperature in solar absorption chiller

The study described in this paper results from the observation that, when dealing with solar-driven absorption chillers, a compromise situation very likely exists between the collector efficiency and the coefficient of performance (COP) of the absorption cycle. An idea of a control strategy pursuing this objective, and thereby increasing the solar fraction for a solar absorption cooling cycle is consequently presented. The advantage of operating the solar chiller on a variable driving temperature is demonstrated. The theoretical analysis considers a solar chiller operated under moderate climate conditions of Poland. The model of the ammonia-water absorption chiller is described in detail, and the main assumptions of the iterative control procedure are explained. The effects of its application are computationally tested for one location and one type of solar collector, for representative days of three months during the cooling season. The results of the simulation are compared with the reference case of fixed driving temperature. According to the simulation results, it is possible to increase the cooling power yield at various levels, up to 34 W per 1 m2 of solar collector, by adjusting the chiller driving temperature throughout the cooling season. The same, it is possible to more than double the cooling effect for some hours, with respect to fixed-temperature control operation.

Modelling and experimental verification of the thermal performance of an active solar heat storage-release system in a Chinese solar greenhouse

An active solar heat storage-release (AHS) system that stores solar energy in a water storage tank can supplement heat to raise the air temperature in Chinese solar greenhouses (CSGs) during cold winter nights. To quantify such heat transfer processes and to improve the performance of AHS systems, a tank temperature model was developed. The model was calibrated and validated, and it can predict water temperatures in the storage tank with an average accuracy of 0.4 °C. The model was used to determine the required solar collector area and storage tank volume under various desired air temperatures in different greenhouses. In two cases, greenhouses with a ground area of 272 m2 and roughly 62 m2 of solar collectors were installed to maintain temperatures above 12 °C under Beijing climate conditions. To facilitate a 1 °C increase in the air temperature set-point, approximately 2 m2 of additional solar collectors and 0.1 m3 of additional storage tanks are needed.

Thermal-economic analysis of modular solar still under Algerian climatic conditions: effect of collector and condensation chamber area

In this paper, a thermal-economic analysis of a modular solar still was investigated. For that, a modular solar still was designed. The collector area and the condensation chamber area effect on the productivity and distilled water cost were examined. Simulations were performed according to meteorological data of Algiers (Algeria) using Liu Jordan method. Results show that the surface area of collector increase increases the evaporated water and distilled water production at the same time. The average annual production passed from 482.35 L for 2 m2 of solar collector to 2083.65 L for 10 m2 of solar collector. On the other side, increasing surface of solar collector decreases the cost of distilled water. The cost of liter of distilled water varies between 0.12 and 0.04$ for 2 and 10 m2 of collector, respectively. Also, when the condensation chamber area increases, the amount of the distillate water produced decreases.

‘Transition’ from successful solo practice to Clinic Director; MSQ'S story

Australia has a very sunny climate, with a very high demand for air conditioning. Implementing solar assisted air conditioning is an ideal option to achieve a high solar fraction which leads to a significant amount of energy and greenhouse gas emission savings. Solar assisted air conditioning systems are environmentally friendly by being constructed in a way that minimises the need for chlorofluorocarbons CFC, Hydro chlorofluorocarbons HCFC or Chlorofluorocarbons HFC refrigerants and by using a low grade thermal renewable energy, therefore, making them energy efficient and environmentally safe. They can be used either as stand-alone systems or with conventional AC, to improve the indoor air quality. Solar cooling is a new and a fast growing technology compared to other fields of solar energy applications. On the other hand most of the current solar cooling applications are demonstration projects in nature; the technologies are advancing yet still need a lot of additional design, planning, development, and research efforts. T now solar assisted air conditioning's main obstacles are the high installation costs, and the lack of knowledge and familiarity with this technology between designers, developers and architects.In this paper a feasibility study is carried out to assess a solar assisted air conditioning system for an office building under three of Queensland's subtropical climates; Rockhampton, Gladstone, and Emerald. The technical aspects of a proposed solar cooling system are investigated. Cooling load profile for a proposed reference building was obtained using TRNSYS software under the influence of these different climates. An electric vapour compression pump, with 2.5 coefficient of performance (COP) for cooling is used as a reference system to assess the primary energy consumption, assuming 80% of primary energy consumed by the reference conventional system is replaced by solar energy. The results of analysing the proposed system indicated that an 80% of the primary energy savings can be achieved by installing 50 m2 of solar collectors and 1.8 m3of hot water's storage tank under the three selected climates.

Improving ice productivity and performance for an activated carbon/methanol solar adsorption ice-maker

The paper addresses the factors that can improve the performance of an activated carbon/methanol intermittent solar adsorption ice marker. It optimizes the ice maker under Dhahran climate with the MATLAB program to improve the performance and to increase the ice production per day per square meter of the solar collector. The optimizing results show that 14.1kg of activated carbon NORIT RX3-Extra per m2 of solar collector, double glazing cover, thin stainless steel absorber tubes with selective coating, suitable monthly collector tilt angle and suitable time for starting the cycle improve the performance. Moreover, the system can produce from 5kg up to 13kg of ice per day per m2 of collector area with improved solar coefficients of performance (SCOP) of 0.12 and 0.24 in the hot and the cold days, respectively. The optimized solar refrigerator is of benefit to further application and producing ice in grid-off rural zones.

Cause rare de compression médullaire

The paper addresses the factors that can improve the performance of an activated carbon/methanol intermittent solar adsorption ice marker. It optimizes the ice maker under Dhahran climate with the MATLAB program to improve the performance and to increase the ice production per day per square meter of the solar collector. The optimizing results show that 14.1 kg of activated carbon NORIT RX3-Extra per m2 of solar collector, double glazing cover, thin stainless steel absorber tubes with selective coating, suitable monthly collector tilt angle and suitable time for starting the cycle improve the performance. Moreover, the system can produce from 5 kg up to 13 kg of ice per day per m2 of collector area with improved solar coefficients of performance (SCOP) of 0.12 and 0.24 in the hot and the cold days, respectively. The optimized solar refrigerator is of benefit to further application and producing ice in grid-off rural zones.

Numerical simulation and experimental validation of a controlled flow solar water disinfection system

A controlled flow solar thermal disinfection system was manufactured, tested and numerically investigated. The system is simply constructed of a 2.34 m2 flat-plate solar collector at which the outlet flow temperature is controlled by a solenoid valve to a disinfection temperature. The outlet hot disinfected water is used to preheat the inlet untreated water through a heat exchanger. Different disinfection temperatures are considered with their corresponding heating periods of time. The system is numerically simulated to investigate their annual performance and life cycle savings. The simulation model is validated by measured data with close agreement. It is obtained that the considered simple system working at 60°C disinfection temperature can daily produce 171 l of clean water by m2 of solar collector where it reduces into about 39 l/m2 at 90°C. That corresponds to 81.5 and 1.1 l/m2 per kWh of incident solar radiation respectively. The disinfected liter of water can cost about US$ 0.00001 along the syste...

Application of direct steam generation into a solar parabolic trough collector to multieffect distillation

In this paper, the application of the direct steam generation into a solar parabolic trough collector to multieffect distillation is proposed and economically evaluated. The thermal fluid of the solar field is pure water, which boils as circulating along the solar collectors. The steam generated drives a multieffect distillation unit. This solar distillation system is compared with multieffect plants connected to a conventional parabolic trough collector field, and with fossil fuel powered distillation plants. Different parameters are analysed, the plant capacity and performance ratio, the cost of conventional thermal energy, the cost of the solar collectors, and the annual average of the fresh water obtained per m2 of solar collector. Results obtained are useful in finding the most suitable conditions in which solar energy could compete with conventional energies in solar desalination.

Energy analysis and solar energy development in Cyprus

This article reviews the application of solar energy technology in Cyprus and presents an energy analysis, including the use of solar energy, in the island. Cyprus has no conventional sources of energy and is dependent on imported oil. However, its geographical position is such that it is one of the countries where the potential for solar energy utilisation is very high. Cyprus began manufacturing solar water heaters in the early 1960s and today it produces more than 30 000 m2 of solar collectors yearly. It is estimated that more than 130 000 solar water heaters are in operation, which provide the equivalent of 9% of the total electricity consumption in the island, and corresponds, approximately, to 4% of the national energy consumption. However, the use of solar energy for space heating and cooling provides a further challenge because it does not appear to be economic under the climatic conditions and system design practices currently prevailing in Cyprus. The article provides a statistical analysis of the energy demand and identifies areas of further growth for solar energy technology.

A high-flux low-temperature solar collector

A preliminary study of a solar-heated low-temperature space-heating system with seasonal storage in the ground has been performed. The system performance has been evaluated using the simulation models TRNSYS and MINSUN together with the ground storage module DST. The study implies an economically feasible design for a total annual heat demand of about 2500 MWh. The main objective was to perform a study on Anneberg, a planned residential area of 90 single-family houses with 1080 MWh total heat demand. The suggested heating system with a solar fraction of 60% includes 3000 m2 of solar collectors but electrical heaters to produce peak heating. The floor heating system was designed for 30°C supply temperature. The temperature of the seasonal storage unit, a borehole array in crystalline rock of 60,000 m3, varies between 30 and 45°C over the year. The total annual heating costs, which include all costs (including capital, energy, maintenance etc.) associated with the heating system, were investigated for three different systems: solar heating (1000 SEK MWh−1), small-scale district heating (1100 SEK MWh−1) and individual ground-coupled heat pumps (920 SEK MWh−1). The heat loss from the Anneberg storage system was 42% of the collected solar energy. This heat loss would be reduced in a larger storage system, so a case where the size of the proposed solar heating system was enlarged by a factor of three was also investigated. The total annual cost of the solar heating system was reduced by about 20% to about 800 SEK MWh−1, which is lower than the best conventional alternative.