Solar Heat Input Research Articles

Development of a solar-ocean based integrated plant with a new hydrogen generation system

Considering the global urgency to decrease carbon emissions and shift to sustainable energy sources, combining solar and other renewables with hydrogen generation appears to offer an appealing answer. The combination of solar and ocean energies with hydrogen production, therefore, offers a great potential to improve energy efficiency and create a feasible route towards zero-emission energy systems. A new hybrid photoelectrochemical (PEC)-conventional electrolysis system was designed and incorporated into the proposed multigeneration system. The hybridized reactor combines the benefits of PEC and conventional electrolysis by using a developed bipolar anode to produce hydrogen continuously, even when there is no solar radiation. The main aim of this research is to investigate the integrated power process that utilizes solar power for several uses, such as generating electricity, producing freshwater, and synthesizing hydrogen. The proposed research involves integrating several components, including a solar through collector system, a combination of power cycles (steam and organic Rankine cycles), a multi-effect desalination (MED) unit, a new hybrid electrolyzer system, a wave energy system, and a hydrogen storage and refuelling station. The main outputs include 2.05 kg/s freshwater production, 0.125 kg/s hydrogen production, 16,284.24 kW net work rate, and 95,068 kW solar heat input. The highest exergy destruction rates were found in the solar collector (56,194.8 kW) and turbines T1 and T2 (6019.9 and 4627.6 kW). The overall energy and exergy efficiencies of the proposed system are obtained to be 15.83 % and 16.61 %, respectively.

Manure temperature prediction for slurry storage in Sweden: Model validation including effects of shading, snow cover and mixing

Measuring and modelling manure temperatures are crucial for estimating greenhouse gas emissions from liquid manure storage. The manure temperature was recorded at various depths in two swine slurry storage tanks situated in Vallentuna (VA) and Örsundsbro (OR) in Sweden. These data were used to assess the effectiveness of a revised mechanistic model for estimating manure temperatures, which incorporates the effects of wall shading, snow cover, and manure input mixing. The average manure temperatures were higher than air temperatures in the summer and fall. This indicated that using air temperature would result in an underestimation of methane emissions when applying the 2019 IPCC Refinement methodology. The revised model estimated manure temperatures for spring, summer, fall, and winter as 4.8, 16.1, 7.8, and 2.6 °C at the VA tank and 11.6, 17.1, 9.5, and 3.6 °C at the OR tank. The root mean square errors between daily simulated and observed temperatures in the summer decreased in both tanks due to incorporating shadow effect into the revised model. Fall estimates did not improve, possibly because of uncertainties from slurry removal and higher precipitation inputs. Sensitivity analysis indicated that solar radiative heat input was reduced with higher tank walls and smaller tank diameters when applying the revised model. Wall shading may influence manure temperatures in tanks with small diameters at high-latitude locations. This study offers insights into understanding the relationship between manure temperatures and its thermal balance influenced by latitude, storage design, snow cover and mixing, and its implications for accurately estimating methane emissions.

Thermo-economic analysis and multi-objective optimization of solar aided pumped thermal electricity storage system

The concept of solar energy aided pumped thermal electricity storage (Solar-PTES) was proposed to improve the round-trip efficiency, as well as the solar energy utilization efficiency. The thermodynamic model was developed for such Solar-PTES system with the nominal electricity input of 5 MW and the nominal storage capacity of 6 equivalent hours. Taking the round-trip efficiency, energy density and levelized cost of storage as indicators for system performance, the effects of main design parameters were investigated, including that of main components performance parameters and cycle state parameters. The multi-objective optimization algorithm was applied for optimizing three performance metrics and the trade-off analysis was performed. The results indicates that the round-trip efficiency drops with the growing energy density, while the levelized cost of storage firstly decreases as the round-trip efficiency drops and then slightly rises. The minimum case of levelized cost of storage is selected for investigation. In that case, solar heat input is 5.05 MW and solar energy utilization efficiency of Solar-PTES system is 35.7 %. The nitrogen mass flow rate is 27.54 kg/s. The round-trip efficiency, energy density and levelized cost of storage for Solar-PTES system are 68.1 %, 16.63 kWh/m3 and 0.143 ± 0.023 $/kWh, respectively.

Thermodynamic and economic analysis of a supermarket transcritical CO2 refrigeration system coupled with solar-fed supercritical CO2 Brayton and organic Rankine cycles

Aiming to reduce the use of conventional energy sources, alternative methods should be applied in order to cover society’s needs. In this context, in the present study, the operation of a transcritical CO2 commercial refrigeration unit is investigated, coupled with two power production cycles. The first cycle is a supercritical CO2 Brayton system that is supplied with heat by a solar field including parabolic trough collectors, while the second one is an organic Rankine cycle, utilizing as a heat source the low enthalpy CO2 exiting the first cycle. The novelty of this system is attributed to the combination an advanced transcritical CO2 refrigeration system with power production cycles that operate under the optimal conditions, as well as to the reason that the operation of the refrigeration unit is independent from the solar energy, since it can provide refrigeration output regardless of the solar heat input. The results prove that the increased number of solar collectors leads to more advantageous power production results, although with higher capital costs. Furthermore, greater energy production is noted when the ambient temperature is lower and abundant solar power is available. For the case of installing five solar collectors and an organic Rankine cycle, it is found that the annual energy production of the total system is 173.72 MWh, while the annual energy consumption of the refrigeration unit is 466.66 MWh, meaning that 37.23 % of energy savings are achieved annually. For the same configuration, according to the life cycle cost analysis, the capital cost is found equal to 243.72 k€, leading to a payback period of 7.6 years. By the end of the project’s lifetime, the operation of the installed system returns 298.42 k€ to the investor.

Computational fluid dynamics-based parametric study on the performance of solar air heater channel.

Computational fluid dynamics (CFD) plays a prominent role in the design and development of solar air heaters. The previous investigations have lagged in using a radiation model for the solar heat input; instead, most of the researchers simulated a constant heat flux model. Moreover, an extensive study on the geometrical and boundary conditions like confinement and transition length, suction, and blowing effects has not been studied. The present investigation deals with the aforementioned effects on the flow and heat transfer characteristics of the SAH channel, which is designed for residential space heating. The finite volume-based solver Ansys Fluent is used for finding the field variables. The confinement height is varied from 25 to 150mm, and the transition length is varied from 250 to 1000mm. The suction and blowing effect is investigated by changing the flow direction across the channel. Even though the temperature rise is less significant with respect to confinement height and transition length, the effective efficiency increases with decreasing channel height and increasing transition length. In general, blowing of air across the channel gives better performance than suction. When comparing them, the influence is less in temperature rise and more in pressure drop for the channel height of 25mm, whereas the channel height of 150mm has better influence in temperature rise and less influence in pressure drop.

Tunable Intracrystal Cavity in Tungsten Bronze‐Like Bimetallic Oxides for Electrochromic Energy Storage (Adv. Energy Mater. 5/2022)

Electrochromic Energy Storage In article number 2103106, Guofa Cai, Pooi See Lee and co-workers report that Nb18W16O93 nanomaterials with superstructure motifs show fast Li+ intercalation–deintercalation kinetics and robust stability for both electrochromic and rechargeable energy storage applications. A complementary smart window is further fabricated based on the Nb18W16O93 film, which can dynamically regulate the sunlight and solar radiant heat input of buildings while electrical energy can be stored in the smart window, providing a multifunctional system consisting of electrochromism, energy storage and an indicator.

Estimating Smart Wi-Fi Thermostat-Enabled Thermal Comfort Control Savings for Any Residence

Nowadays, most indoor cooling control strategies are based solely on the dry-bulb temperature, which is not close to a guarantee of thermal comfort of occupants. Prior research has shown cooling energy savings from use of a thermal comfort control methodology ranging from 10 to 85%. The present research advances prior research to enable thermal comfort control in residential buildings using a smart Wi-Fi thermostat. “Fanger’s Predicted Mean Vote model” is used to define thermal comfort. A machine learning model leveraging historical smart Wi-Fi thermostat data and outdoor temperature is trained to predict indoor temperature. A Long Short-Term-Memory neural network algorithm is employed for this purpose. The model considers solar heat input estimations to a residence as input features. The results show that this approach yields a substantially improved ability to accurately model and predict indoor temperature. Secondly, it enables a more accurate estimation of potential savings from thermal comfort control. Cooling energy savings ranging from 33 to 47% are estimated based upon real data for variable energy effectiveness and solar exposed residences.

Global equivalent slab thickness model of the Earth’s ionosphere

The shape of the vertical electron density profile is a result of production, loss and transportation of plasma in the Earth’s ionosphere. Therefore, the equivalent slab thickness of the ionosphere that characterizes the width of vertical electron density profiles is an important parameter for a better understanding of ionospheric processes under regular as well as under perturbed conditions. The equivalent slab thickness is defined by the ratio of the vertical total electron content over the peak electron density and is therefore easy to compute by utilizing powerful data sources nowadays available thanks to ground and space based GNSS techniques. Here we use peak electron density data from three low earth orbiting (LEO) satellite missions, namely CHAMP, GRACE and FORMOSAT-3/COSMIC, as well as total electron content data obtained from numerous GNSS ground stations. For the first time, we present a global model of the equivalent slab thickness (Neustrelitz equivalent Slab Thickness Model – NSTM). The model approach is similar to a family of former model approaches successfully applied for total electron content (TEC), peak electron density NmF2 and corresponding height hmF2 at DLR. The model description focuses on an overall view of the behaviour of the equivalent slab thickness as a function of local time, season, geographic/geomagnetic location and solar activity on a global scale. In conclusion, the model agrees quite well with the overall observation data within a RMS range of 70 km. There is generally a good correlation with solar heat input that varies with local time, season and level of solar activity. However, under non-equilibrium conditions, plasma transport processes dominate the behaviour of the equivalent slab thickness. It is assumed that night-time plasmasphere–ionosphere coupling causes enhanced equivalent slab thickness values like the pre-sunrise enhancement. The overall fit provides consistent results with the mid-latitude bulge (MLB) of the equivalent slab thickness, described for the first time in this paper. Furthermore, the model recreates quite well ionospheric anomalies such as the Night-time Winter Anomaly (NWA) which is closely related to the Mid-latitude Summer Night-time Anomaly (MSNA) like the Weddell Sea Anomaly (WSA) and Okhotsk Sea Anomaly (OSA). Further model improvements can be achieved by using an extended model approach and considering the particular geomagnetic field structure.

Design Guidelines for Thermal Comfort and Energy Consumption of Triple Glazed Fluidic Windows on Building Level

AbstractThere has been a growing trend for buildings with large glazing size. As a trade‐off, this comes with enhanced solar heat input and/or reduced thermal insulation. Several approaches are being followed to reduce the energy consumption in these buildings, including the prolific field of smart windows. In a previous report, a fluidic window device for thermal harvesting and air‐conditioning was introduced. Using this example, the impact of a building's window‐to‐wall ratio on the triple glazed fluidic window's energy consumption and user thermal comfort is evaluated, providing design guidelines for large‐scale implementation of such smart windows with real‐world buildings. The analysis shows that the proposed window design reduces the primary energy demand as compared to using a conventional air‐conditioning system. Building simulation results indicate that the system enables satisfying thermal comfort for buildings with different window‐to‐wall ratios. Although a higher window‐to‐wall ratio improves the heat pump efficiency, it requires more heating and cooling energy. On‐device photovoltaic modules may be used for changing this relationship. In this case, the proposed device may become self‐sufficient once the transfer efficiency is high enough. It is argued that similar considerations should be applied to other types of smart window technologies.

Microvessel‐Assisted Environmental Thermal Energy Extraction Enabling 24‐Hour Continuous Interfacial Vapor Generation

Interfacial solar evaporators have great potential for clean water production; however, their evaporation performance relies greatly on the solar illumination condition, which is restricted by daily sunshine time and climates. Here, a wood-based vapor generator in pyramid structure is fabricated to achieve efficient water evaporation under dark condition (0 kW m-2 ) through efficient extraction of environmental thermal energy. The microvessels of wood provide fast water transportation whereas the tailored pyramid surface structure enables efficient evaporative cooling for extracting energy from the environment. The method enables fast water evaporation without the need of solar heat input. We demonstrate a vapor generation rate of up to 2.15 kg m-2 h-1 under dark condition (0 kW m-2 ), which is even 1.4 times faster than the theoretical limit of conventional solar thermal evaporators working under 1 sun (1 kW m-2 ) illumination condition. During the 24-h continuous evaporation test, the evaporator presented a daily vapor generation rate of up to 50.8 kg m-2 day-1 and 60.7 kg m-2 day-1 on cloudy and sunny day, respectively, offering a novel approach for the development of 24-h full-time water evaporators for seawater desalination and wastewater treatment.

A Synthesis of Observations and Models to Assess the Time Series of Sea Ice Mass Balance in the Beaufort Sea

AbstractOver the past four decades, there has been a substantial thinning of the summer sea ice cover in the Beaufort Sea. Variations in sea ice mass balance reflect these changes and give insight to the environmental forcings which caused them. In this work, the time series results from eight Lagrangian mass balance sites that operated in the Beaufort Sea over the years 1997–2015 are analyzed. Direct measurements from the sites are combined with estimates of ice/ocean heat input to examine the roll of solar heating on ice loss, growth, and melt rates. Comparisons between ice and snow conditions and mass balance event timing, for example, surface and bottom melt onset, melt peak, and melt end, are also made. From the late 1990s to the present, a general increase in bottom melting and solar heat input to the upper ocean was observed. All sites showed a net loss of ice (ranging from 29 to 271 cm), and all but one site saw the majority of this loss from bottom melting. Bottom melt onset occurred within a relatively narrow 13‐day window between 1 and 13 June at all sites. The amount of observed bottom melt was also related to the heat deposited in the ocean available for melting, underscoring the increasingly important role of ocean thermodynamics in determining sea ice mass balance.

Changing ice and changing light: trends in solar heat input to the upper Arctic ocean from 1988 to 2014

AbstractThe Arctic sea-ice cover has undergone a significant decline in recent decades. The melt season is starting earlier, ice is thinner and seasonal ice dominates. Here we examine the effects of these changes on the solar heat input to the upper ocean in ice-covered Arctic waters from 1985 to 2014. Satellite observations of ice concentration, onset dates of melt and freeze-up and ice age, are combined with ice thicknesses from the PIOMAS model and incident solar irradiance from reanalysis products to calculate the contributions of open ocean and ice to the solar heat input in the upper ocean. Of the total, 86% of the area has positive trends for solar heat input to the ocean through leads due to decreases in ice concentration. Only 62% of the area shows positive trends of solar heat input to the ocean explicitly through the ice. Positive trends are due to thinning ice, while negative trends occur in regions where the ice-free season has lengthened. The annual total solar heat input to the ocean exhibits positive trends in 82% of the area. The spatial pattern of the cumulative annual total solar heat input is similar to the pattern of solar heat input directly to leads.

Assessing geothermal/solar hybridization – Integrating a solar thermal topping cycle into a geothermal bottoming cycle with energy storage

Geothermal and concentrating solar power (CSP) technologies typically use heat at different temperatures in their commercial deployments. This enables a technically viable hybridization of a solar topping cycle and a geothermal bottoming cycle at locations where both resources are available. In this article, an underperforming geothermal power system based at Burley, Idaho is used as a baseline to investigate the technical and economic potential of such a hybrid cycle. A direct thermal energy storage (TES) system is also integrated to overcome the intermittency of the solar resource. Design and off-design behavior of key components are modelled to simulate the annual performance of the hybrid system on an hourly basis. The sizing of the solar field and thermal storage is investigated and is seen to significantly impact the annual electricity generation and efficiency. Various cost scenarios for the solar field and thermal energy storage are investigated. An economic metric – levelized cost of electricity (LCOE) – is used to optimize the solar field sizing and TES capacity. The hybrid plant converts the additional solar heat input into additional work with an efficiency of 32.9%. Retrofitting a geothermal plant with solar and eight hours of energy storage can achieve an LCOE of 0.136 $/kWhe in current cost scenarios and 0.081 $/kWhe in a future cost reduction scenario. Although the hybrid system cannot directly compete with current PV systems without batteries, it has an LCOE 32% lower than that of a PV-battery system. This paper provides insights into the research and development of the future grid with a high renewable energy penetration and encourages further study of energy hybridization for improved efficiencies and economics.

Influence of Solar Radiation Heat Input into Room on Level of Economically-efficient Thermal Protection of Building

Techniques for choosing an energy and economically feasible thermal protection of buildings in the climatic conditions of Moscow are discussed earlier. An important basis of these techniques is that it was possible to identify the thermal parameters on the basis of which the generalization of the basic energy and economic indicators of the building, depending on its thermal protection, was carried out. The methods were tested for buildings whose working day lasts from 9 am to 6 pm with various internal heat generation. In this case, it was believed that solar radiation is completely obscured. From consideration of the effect of heat gains on energy-efficient thermal protection, it was found that with increasing heat gains, the load on heating systems decreases regardless of the level of heat protection, and the load on the room cooling systems increases more with higher thermal protection than with low thermal protection. However, there are buildings of a number of functional purposes in which solar radiation is partially obscured or not obscured at all. These include some commercial, residential and other buildings. Accounting for heat gains from solar radiation, with variable intensity throughout the year, makes significant adjustments to the choice of the level of thermal protection. This is due to the fact that often cooling of the room is required during periods when the outside air temperature is below the maximum allowable temperature of the room. During these periods, enhanced thermal protection is an obstacle to the natural outflow of heat from the premises. Calculations showed that the higher the heat gain from solar radiation, the smaller the proportion of buildings it is energetically feasible to warm according to the basic standards stipulated in SP 50.13330.2012. And although it is not energetically feasible to carry out thermal insulation for sanitary and hygienic requirements, the conclusions about the benefits of building insulation with reduced heat transfer to the walls and coatings of a building are economically significant. It is also important that when identifying an economically feasible thermal protection of a building, it is necessary to take into account all the components of financial expenses that are affected by the thermal protection of a building. The calculations also showed that an increase in the cost of heat and electricity over time changes the thermal performance of buildings for which this or that thermal protection is economically feasible.

Prototype latent heat storage system with aluminum-silicon as a phase change material and a Stirling engine for electricity generation

In this work, we present the design and experimental results of a prototype latent heat thermal energy storage system. This prototype used 100 kg of aluminum-silicon as a phase change material with embedded heat pipes for effective heat transfer, a valved thermosyphon to control heat flow out of the thermal storage system, and a Stirling engine to convert heat to electricity. We tested this system for 11 simulated days of operation; each day included charging of the thermal storage tank, simultaneous electricity generation with heat input, and electricity generation from stored heat alone. On each simulated day, we set the engine to a different power level, allowing us to investigate the response of heat pipes and our valved thermosyphon to part-load conditions. The prototype demonstrated a maximum efficiency of 18.5% in converting stored heat to electricity, at a maximum power output of over 1kWe. Extending these results to a commercial scale system with solar heat input, our modeling indicates that a discharge efficiency of over 30% and an annual efficiency of 18% could be achieved. This performance represents an advancement in established efficiency for any system that combines latent heat storage with electricity generation, and demonstrates that this system has potential for future commercial development.

Performance maximization of a solar aided power generation (SAPG) plant with a direct air-cooled condenser in power-boosting mode

Solar aided (coal-fired) power generation (SAPG) technology has been approved to be an efficient way to use solar energy for power generation. However, most solar-rich areas are often short of cooling water supply, especially in China. The air-cooled condenser could alleviate this issue effectively for power plants in these areas. In this paper, a solar aided power generation with direct air-cool condenser (SAPG + ACC) plant is studied and optimized to maximize its performance. Due to the addition of solar heat in an SAPG plant, the exhaust steam flow rate leaving the turbine changes, especially in power-boost mode, which affects the turbine exit pressure and deviates the condenser from its designed operating condition. To achieve maximum net power output, the correlation among the optimum (turbine) exit pressure (OEP), the solar heat input and the ambient temperature, is obtained in this study. The annual plant's performances with four proposed operating strategies of the air-cooled condenser are compared and analyzed. The results show that for an SAPG + ACC plant, the operating Strategy.3, i.e. operated with the hourly OEP is the optimal one, resulting the plant has annual solar-to-electricity efficiency (SEE) of 17.82% and its levelized cost of electricity (LCOE) is of 0.09 $/kWh.

The influence of the solar radiation heat input into the room on the level of energy-efficient thermal protection of the building

The task of increasing the energy efficiency of external enclosing structures is often considered as the need to increase their heat transfer resistance. At the same time, the main indicator of this efficiency is the heat consumption reduction for heating of the buildings having high thermal protection. Despite the fact that Russia is a rather cold country with a long heating period in most of its territory, the lack of accounting the cold consumption in warm period of the year leads to wrong understanding by the specialists of the energy expediency of the building thermal protection level. In today’s world, more and more buildings, which have been built, house the civil technologies with high heat emissions, i.e. administrative and office, entertainment, training, shopping and other buildings. These buildings require high energy consumption for cooling, which is often necessary even during the heating period. Taking into account the heat input from the solar radiation with variable intensity throughout the year, the thermal protection level is subject to significant corrections. This is due to the fact that often the cooling of the room is required during the periods when the outdoor temperature is below the maximum allowable room temperature. During these periods, the enhanced thermal protection is an obstacle to the natural heat outflow from the premises. The calculations showed that the higher is the solar radiation heat input, the smaller is the part of energetically feasible buildings according to the basic norms prescribed by the SP 50.13330.2012. And although the sanitary and hygienic requirements show no reasons of the building heat insulation from the energy point of view, the conclusions about the profitability of the building insulation with a reduced basic resistance to heat transfer of walls and coatings of the building are economically significant.

Al-Abdaliya integrated solar combined cycle power plant: Case study of Kuwait, part I

Abstract Kuwait is planning to develop a solar project using a 60 MWe parabolic trough collector in Al- Abdaliya. This will be part of a 280 MWe Integrated Solar Combined Cycle (ISCC) System, which will be the first of its kind and size in Kuwait. The objective of this paper is to develop a mathematical model of a typical ISCC system using Engineering Equations Solver (EES), to evaluate the performance of such commercial ISCC power plants. A sensitivity analysis has been carried out to investigate the effect of selected parameters on the performance of the planned ISCC power plant. Results show that the efficiency of Abdaliya ISCC power plant could reach more than 66% which is 20–100% higher than that of the current conventional power plants in Kuwait. The plant output power is also a strong function of solar heat input, it could reach 290 MWe at solar heat input of 75 GJ/s. The annual fuel saving and emissions reduction are more pronounced in case of adding thermal energy storage than that of increasing its solar fraction from 0.2 to 0.3. The expected annual benefits could support the decision-makers to accelerate the adoption of ISCC power plants in Kuwait.

Determination of optimal dimensions of fixed shadowing systems (pergolas) to reduce energy consumption in buildings in Romania

Depending on the season, the sun light entering a building has a varying impact upon the energy consumption of the building. Thus, during winter, the sunlight reaching the façade of a south-oriented building can provide passive solar heating, hence reducing the energy consumption required to heat the building. Contrary to this, during summer, the sun rays penetrating the building mainly through windows oriented towards the south lead to excessive accumulation of heat. To diminish the thermal lack of comfort, it is necessary to increase energy consumption required to cool the building. The fixed shadowing devices such as pergolas, when well designed, are able to significantly reduce the energy consumption required to cool the building during summer and also to allow for the energy contribution from the solar beams, during winter. Shadowing has always been recommended as a passive way to diminish solar heat input in constructions. In order to reach this aim, i.e. of reducing energy consumption in buildings in Romania, the present paper presents the optimal dimensions of fixed shadowing devices, namely of pergolas.

Thermo-Economic Analysis of a hybrid solar micro gas turbine power plant

This work proposes a hybrid system based on a micro-gas turbine plant integrated with a solar field either to provide a part of the heat addition or to totally replace the combustor in the case that the only solar heat input is enough to ensure that the working fluid reaches the turbine inlet temperature. The system can operate in a pure combustion mode when solar irradiance is weak or completely absent during some hours in the day or seasons. The analysis is based on the simulation of the overall plant by the Thermoflex software, a modular program that allows assembling model with several components.In particular, many calculations have been performed to simulate the solar-assisted cogenerating plant in different operating conditions in order to identify the optimum sizing of the solar system which reduces the annual costs or the fuel consumption and, consequently, the CO2 emissions. Numerical results are compared with the data available from standard micro gas turbine plant. Finally, an economical evaluation by calculation the SPB (simple pay back) is obtained for all test cases to evaluate the benefit from Italian State incentives.