Analysis of a photovoltaic-thermal collector-based energy system for powering multi-unit residential buildings

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

The effect of an enclosure retrofit on air leakage rates for a multi-unit residential case-study building

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.

• Unified techno-economic assessment framework solar district heating systems. • Integration of solar thermal/thermal energy storage and PV/battery/heat pumps. • Solar fraction dominated by solar collectors area and thermal energy storage size. • Seasonal thermal energy storage needed for high solar fractions in Munich/Copenhagen. • Optimal sizing of solar district heating highly sensitive to electricity prices. The present work investigates how the relative sizing of thermal (solar collectors, thermal energy storage – TES tank) vs electrical (PVs, heat pumps, batteries) conversion pathways of a generalized solar district heating (SDH) system affects its (a) environmental (solar fraction) and (b) economic (levelized cost of heating – LCOH ) performance. For this purpose, a novel, unified techno-economic assessment framework is applied for a 1,000 persons community in Athens, Munich and Copenhagen for maximum collectors/PV areas of 10,000 m 2 . For SDH without PVs/batteries, 100 % solar fractions are achieved in Athens by diurnal storage and collector areas above 6,000 m 2 . However, maximum collector areas and seasonal storage is necessary in Munich /Copenhagen to achieve maximum solar fractions (about 50–60 %). Because of higher electricity prices in Athens, cost-optimal systems do not include heat pumps. In Munich/Copenhagen, heat pumps are cost-effective for lower solar fractions and lower electricity prices. The addition of PV/batteries results in small increase in the solar fraction, which is nevertheless mainly affected by the collectors area. With electricity exports, cost-optimal systems include maximum PV areas without batteries exporting electricity and minimum required collector areas/tanks for targeting the desired solar fraction. In Munich/Copenhagen, small-sized heat pumps are cost-effective for lower electricity prices. Whereas batteries are not cost-effective, they are necessary for higher solar fractions in these two cities. Without electricity exports, adding PV/batteries results in higher LCOH , thus thermal conversion is cost-optimal. Overall, electricity prices and PV renumeration schemes significantly influence optimal relative sizing of thermal vs electrical pathways of SDH systems.

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.

A review of factors affecting occupant comfort in multi-unit residential buildings

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.

Economic analysis and optimization of household solar heating technologies and systems

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.

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

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

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

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

Reply to comments by T. Muneer

A new normalized model is developed to quantify and explore trends in coincidence of supply and demand in generic intermittent energy systems as key design and operating parameters are varied. This novel model is applied to seasonal-transient simulations for a solar-thermal powered adsorption system with and without heat recovery to investigate the coincidence between the solar-supplied cooling power and cooling load in terms of seasonal solar and loss fractions. Additionally, the system's basic performance trends are investigated as a number of parameters are varied. Results for the conditions explored include the following. The solar fraction increases and the loss fraction decreases with increases in storage capacity, and both fractions decrease with increases in maximum bed temperature. The required evacuated tube collector area is smaller than the flat plate collector area while the required mass of adsorbent is independent of collector and adsorption cycle types. Simulation results also show the effects of operating conditions and several design parameters on the system's COP.