Increase In Solar Fraction Research Articles

Performance comparison of air source heat pump coupling with solar evacuated tube water heater and that with micro heat pipe PV/T

Air source heat pump (ASHP) has been generally regarded as energy saving devices for winter heating, yet for low-income households, the operational costs for heating in low-temperature conditions may be prohibitively high. Solar evacuated tube water heater (SETWH) and photovoltaic/thermal are economical solar energy conversion devices. Integrating them into ASHP has been proven globally to significantly reduce heating costs. However, a performance comparison between the SETWH combined with ASHP (SETWH-ASHP) and of micro heat pipe photovoltaic/thermal (MHP-PV/T) combined with ASHP (MHP-PV/T-ASHP) heating systems remains unexplored. Therefore, for a 120 m2 building with underfloor heating water pipe, SETWH-ASHP and MHP-PV/T-ASHP heating systems were respectively developed on the TRNSYS software platform. Their accuracy was confirmed using prior experimental data, followed by performance simulation for the heating season. The result is that MHP-PV/T-ASHP heating system outperformed SETWH-ASHP heating system, showing a 19 % increase in solar fraction, a 2.2 boost in system energy efficiency ratio, a 12.3 % rise in primary energy saving rate, a 0.9-year shorter payback period, and a reduction of 494.7 kg in CO2 emissions over the heating season. The results offer practical guidance for the promotion and application of heating systems that combine efficient and low-cost solar conversion devices with ASHP.

Analysis of a variable auxiliary volume predictive-controller for an auxiliary-energy producer with a stratified solar thermal combistorage

Status quo controllers of auxiliary-energy system in a hybrid thermal energy system use a simple dual-auxiliary-zone method where the maximum temperature and maximum volume of the space heating (SH) and domestic hot water (DHW) loads on highest consumption day in a year are utilized. Due to this simple control, there are high storage losses in the winter period an also less storage space available for the renewable production. In this paper, the authors propose a novel predictive control strategy with the use of stratified thermal storage. The control strategy is further, in terms of as ideal simulation study, investigated for a decentral thermal energy system in southern Germany with solar thermal collectors and a gas boiler auxiliary energy system for a stratified combistorage with DHW and SH loads. The obtained results in a Sonnenhaus standard single-family house show that the auxiliary energy input is reduced by 650 kWh (6%) annually with a maximum of 190 kWh reduction in March. Moreover, in the month of March, a 5% increment in terms of solar thermal fraction and a 5.5% decrement in terms of the gas boiler fraction is achieved. And by better use of the storage, especially during the winter months (November to March), a 16–20% reduction in storage losses is achieved. Annually, 2.2% reduction of gas boiler fraction, 4.6% reduction of storage loss and 1.8% increase of solar fraction are attained.

Performance, economic and environmental assessment of solar cooling systems under various climates

Solar cooling systems are gaining more attention as eco-friendly cooling technology, which could be an alternative to the conventional vapor compression cooling one to meet the growing demand of space cooling. This paper proposes the investigation of different solar cooling systems, namely: solar absorption, solar adsorption, photovoltaic and photovoltaic thermal cooling systems on the basis of performance, economic and environmental aspects. The main objective is to identify the most favorable system depending on climate condition and solar fraction. Moreover, a numerical simulation is performed on EnergyPlus software to determine the cooling loads of a typical office building for air-conditioning purpose. Performance, economic and environmental analyses are carried out in terms of key indicators, such as solar coefficient of performance (SCOP), levelized cost of cooling (LCOC), discounted payback period (DPP), and life cycle climate performance (LCCP).The results showed that the increase of solar fraction impacts positively the economic and environmental indicators, since this could reduce the LCOC, DPP and LCCP values. Besides, the photovoltaic thermal cooling system exhibits the better performance in all climate conditions with SCOP values ranging from 36% to 52%, depending on climate. Furthermore, the economic findings revealed that the lowest values of LCOC are acquired by using photovoltaic cooling system; varying within the range of 0.056–0.25 €/kWhc, depending on climate. While the lowest DPP values are observed in regions with high solar irradiation using photovoltaic cooling system. Moreover, solar adsorption cooling system was found to be the most environmentally-friendly since it exhibits the lowest LCCP value. In addition, it was found that the increase of ambient temperature and solar radiation results in higher SCOP and lower LCOC and DPP values, especially for solar absorption and solar adsorption cooling systems. The current work is expected to serve as a reference for engineers and designers to select the suitable solar cooling system to be installed according to the target location and solar fraction.

Effect of efficient multi-stage indirect evaporative cooling on performance of solar assisted desiccant air conditioning in different climatic zones.

Over the past decade, different variants of desiccant cooling system integrated with direct/indirect evaporative cooler(s) have been simulated and/or analyzed in specific climatic conditions under rather limited operating parameters and for limited durations of time. Complete seasonal and multi-climate performance analyses of solar desiccant cooling system integrated with efficient, indirect Maisotsenko Cycle based evaporative cooler, having combinational installations at process and/or regeneration sides, is rarely investigated and reported. In the current work, multiple configuration variants of solar desiccant cooling system, integrated with multi-stage indirect evaporative cooling technique based on Maisotsenko Cycle, having a designed cooling capacity of 50 kW are analyzed through a model-based transient simulation approach. Simulations are carried out for a complete typical summer season in northern hemisphere, starting from April to September, using TRNSYS in three different climatic zones including subtropical humid summer (Cfa), hot desert (Bwh) and hot semi-arid (Bsh) conditions. The three selected climatic zones cover around 20% of global world map hosting more than 37% of world population. Each configuration is analyzed in terms of wet bulb and dew point effectiveness using their respective cooling techniques, system’s thermal coefficient of performance, and solar fraction for each climate zone. It is seen that the configuration using IEC at both process and regeneration sides has the highest values of coefficient of performance and solar fraction in all selected climatic zones compared to others. The respective values of coefficient of performance is 2.28 and solar fraction of 23.84% observed in Bwh while coefficient of performance of 2.03 and solar fraction of 23.33% in Cfa; and coefficient of performance of 2.12 and solar fraction of 46.86% in Bsh climatic zones are noted. The increase of solar fraction in hot and arid climates are expected compared to Cfa. While the value of coefficient of performance for such a system is significantly improved and shows promising prospects to efficiently provide thermal comfort during summer seasons.

Economic analysis and optimization of household solar heating technologies and systems

To find an optimal economic solution for single-family solar heating systems, an evaluation model based on the levelized cost of heat (LCoH) is developed. The initial investment and operating costs of typical single-family solar heating systems are determined using case collection and literature study. These data are used to validate the evaluation model. A Python program is developed and used to calculate the LCoH of differently designed solar heating systems. Based on these calculations, the dependence of LCoH on the solar collector area under different heating load intensities, heating terminal units and heated areas are investigated. The optimal solar collector area and the solar fraction are determined for combinations of solar thermal (ST) with four different types of auxiliary heat source was discussed. The results show that LCoH does not necessarily decrease in a solar-assisted household heating system with an increase of solar fraction (SF) compared to a single conventional heat source system. The findings of this study are useful for designers, professionals and government officials to economically optimize the solar heating system for single-family houses.

Techno-economic analysis of hybrid renewable energy system with solar district heating for net zero energy community

A techno-economic analysis of a hybrid renewable energy system, consisting of a solar thermal system, seasonal thermal energy storage (STES), heat pump systems, and district heating network for a net zero energy community has been conducted. Thermal and electric energy performance of the proposed systems were evaluated using detailed simulation models and experimental results of the Jincheon eco-friendly energy town in South Korea. Comparative environmental and economic analyses on two conventional systems that use gas-fired boilers (Case 1) and a centralized heat pump system (Case 2) were also performed. Assessment criteria in the environmental analysis include equivalent CO2 emissions and primary energy savings. The levelized cost of heat, a benefit-cost method and a payback period calculation were conducted to evaluate the economic benefit. The analyses were also conducted with different sizes for system components. Results showed that the increase in solar fraction of the proposed system reduces CO2 emission by up to 61% compared with Case 2 and enhances primary energy savings by up to 73% compared with Case 1. The levelized cost of heat was lower for the proposed system than the conventional systems. The proposed system showed a 6 year payback period and a benefit-cost ratio of 1.7.

The Optimization of Solar Water Heating System Using Hybrid Algorithm (PSO/HJ) for Different Locations of Turkey

In this study, optimum dimensions of Solar Domestic Hot Water System (SDHWS) were determined according to initial capital cost and energy consumption cost in different locations of Turkey. Typical Meteorological Year (TMY) data of 12 different locations which represent climatic characteristics of Turkey were used. Analysis was performed by using Particle Swarm Optimization / Hooke-Jeeves (PSO/HJ) hybrid algorithm which is a part of EnergyPlus®-GenOpt® programs. For each location, optimum number of solar collectors and hot water storage tank volume was determined. Initial investment and energy consumption costs decreased 6.1% for Gaziantep whereas solar fraction increased 42.8% for Ankara. In average, 4.5% decrease in initial investment and energy costs and 35.4% increase in solar fraction were obtained.

Improvement of collection efficiency and solar fraction in solar thermal storage system using a 3-way valve and a 2-stage flowrate control

In the present study, we investigated the effects of a combined system-control method in a solar thermal system; specifically, prevention of temperature reversal plus a reduced circulation rate. A 3-way valve is adopted as a remedy of the temperature reversal in the water storage tank and a 2-stage flowrate is implemented as the flowrate control strategy. To evaluate the effects, we perform five experiments and TRNSYS based simulations with a carefully developed system-control algorithm. As the main result, we experimentally validated that a 3-way valve is effective for the prevention of temperature reversal and a 2-stage flowrate extends the solar energy collection time. Annual simulation results show that the proposed combined method improves the system performances (1.9%p increase of collector efficiency, 2.2%p increase of solar fraction, and 5.3% additional collected energy) compared to the conventional forced circulation system. Our results should be applied to the water storage tank proposed in this study.

Parametric studies of an active solar water heating system with various types of PVT collectors

This study simulated active photovoltaic thermal solar collectors (PV/T) for hot water production using TRNSYS. The PV/T collectors consist of the amorphous, monocrystalline and polycrystalline. The long-term performances for the glazed and unglazed PV/T collectors were also evaluated. In this simulation, the design parameters used were collector area of 4 m 2, collector slope angle of 15 degree and mass flow rate to the collector area ratio of 8–20 kg/hm 2. In addition the tank height between 0.9 m to 1.1 m for unglazed PV/T collectors and 0.9 m to 1 m for glazed collectors, as well as the storage tank volume between 200 and 300 L has been used. The climate parameters used were solar radiation levels range of 4–4.9 kWh/m 2, the mean ambient temperature in the range of 25–28 ∘C. The results of the simulation indicated that there was an increase in solar fraction and electrical power output of the active PV/T hot water system.

Use of variable geometry ejector with cold store to achieve high solar fraction for solar cooling

Concerns over environmental impact of heat pump cooling systems have led to a revival of solar ejector cooling systems. In order to achieve high solar fractions, the common approach is to increase the solar collector area. However, this is costly and does not provide cooling after sunset. This paper uses software modelling to examine the use of variable geometry ejectors and cold stores to increase the annual yield of an ejector system. The study concludes that a variable geometry ejector is able to increase yield by 8–13% compared to a fixed geometry ejector. However, a 46–50% increase in solar fraction is available if a 60 MJ cold store is included compared to a fixed geometry ejector without storage and up to 63% increase in solar fraction is available if a variable geometry ejector and 60 MJ cold store is used. Alternatively, the modelling shows how the solar collector area may be decreased if a cold store is used and this may benefit the capital and operating cost of the system.

Simulation of the behaviour of transparent insulation materials in buildings in northern China

A simulation model has been developed to analyze the potential of the application of transparent insulation for passive solar buildings in northern China. The potential advantages of using transparent insulation materials in buildings are estimated, in which the effects of variations in solar radiation have been taken into account. By simulating the monthly auxiliary energy requirement of the building and the solar fraction variation due to transparent insulation, it is found that if the traditional south brick walls are covered by a 10 cm thickness layer of honeycomb material in the Beijing area, an increase of solar fraction will be around 39%, corresponding to a solar heat gain of around 137 kW/m 2 year.

Effects of auxiliary heater on annual performance of thermosyphon solar water heater simulated under variable operating conditions

A thermosyphon solar water heating system with electric auxiliary heater was simulated using the TRNSYS simulation program. Location of the auxiliary heater, inside the storage tank or connected in series between the system and the user, was studied using the TMY meteorological data for Los Angeles, California. Simulations were performed for two different water load temperatures (60 and 80°C) and for two types of daily hot water volumes (250 and 150 l). Four types of daily hot water consumption profiles were used in the present study, namely; the widely used Rand profile, continuous, evening and morning profiles. Also, the simulation is extended to cover the effects of thermal and optical properties of the flatplate collector and the volume of the storage tank. The results show that if water is drawn on a schedule corresponding to the Rand draw profile, the system operates with higher efficiency when the auxiliary heater is located in the storage tank than when the auxiliary heater is outside the storage tank. When operated with each of the other three draw schedules, however, better performance is achieved by locating the auxiliary heater outside the tank. The increase in solar fraction depends on the load profile and volume, temperature setting, as well as the quality of the collector and the storage tank volume. When the values of the parameters F R( τα) n and F R U L are changed from 0.8 and 16 kJ/h m 2°C to 0.6 and 30 kJ/h m 2°C, the solar fraction decreases by approximately 40–50%.