Simulations of Combined Solar Thermal and Heat Pump Systems for Domestic Hot Water and Space Heating

AbstractThe system combination of solar thermal collectors and heat pumps is a very attractive option for increasing the renewable energy usage at worldwide level for heating and domestic hot water preparation. In this work parallel and series combined solar and heat pump systems are analyzed within the IEA SHC Task44/HPP Annex38 reference conditions for different buildings and a typical Central European climate. Three combined systems have been studied in detail: solar and air source heat pump, solar and ground source heat pump, and exclusively solar source heat pump in combination with an ice storage. Numerical calculations have been performed using two simulation platforms: TRNSYS-17 and Polysun-6®. Comparisons between the two simulation environments have been also provided. Moreover, a reference case without solar has been used to determine the potential efficiency benefits of using solar collectors compared to a system with a heat pump alone in the specified climate and for covering the specified heat load. Simulations presented in this work show that differences in system performance up to 4% can be expected between TRNSYS-17 and Polysun-6® for air source based systems, and higher discrepancies, up to 14% are obtained for ground source based systems. Comparisons between combined solar thermal and heat pump systems with their respective “heat pump only” reference solutions show that the absolute electricity savings of air source are usually higher compared to ground source based systems. Systems using large ice storages are able to reach seasonal performance factors in the range of 5, which is of the order of performance of combined solar and ground source heat pump systems

SOLAR & PELLET HEATING: SPECIFICATIONS FOR HIGH EFFICIENCY SYSTEM DESIGN

Abstract Combined biomass and solar heating systems provide the opportunity for a heat supply of single family houses without the use of fossil energy. Pellet fired boilers play a predominant role within these systems because their standardised combustible allows for the fully automated operation. However, the combination of biomass boilers and solar collectors places special requirements in view of a good system solution. To analyse the proper combination of both technologies three separate projects were carried out at SPF. the main instrument thereby was the Concise Cycle Test method supplemented by preliminary tests of the boiler and subsequent simulations. It was shown that a modulating boiler operation is superior in terms of both, high energetic efficiency and low emissions compared to intermitting boiler operation. But this is only the case if the following requirements are met: Low excess-air factors for the complete modulation range, low envelope losses, a fast adaption of the output power, correct dimensioning of the boiler. Beside the characteristics of the boiler the hydraulic connection and the control is important to reach a good system performance. Mostly for combined biomass and solar heating systems the best solution is a connection of the boiler to the thermal energy store instead of a direct connection to the heating circuit. The requirements that have to be fulfilled for the control of TES charging are: Temperature sensors within the store to control the boiler dependent to the demand for space heating or domestic hot water. In order to control the power modulation of the boiler, the best option is to reduce the volume flow rate of the boiler pump based on an algorithm that takes into account the temperature measured in the TES. Other options are to increase the return temperature of the boiler using a motorized mixing valve, or to reduce the set-temperature for the water leaving the boiler

SolNet:PhD-scholarships and courses on solar heating

AbstractSolNet, founded in 2006, is the first coordinated International PhD education program on Solar Thermal Engineering. The SolNet network is coordinated by the Institute of Thermal Engineering at Kassel University, Germany. The network offers PhD courses on solar heating and cooling, conference-accompanying Master courses, placements of internships, and PhD scholarship projects. A new scholarship project, “SHINE”, will be launched in autumn 2013 in the frame work of the Marie Curie program of the European Union (Initial Training Network, ITN). 13 PhD-scholarships on solar district heating, solar heat for industrial processes, as well as sorption stores and materials will be offered, starting in December 2013. Additionally, the project comprises a training program with five PhD courses and several workshops on solar thermal engineering that will be open also for other PhD students working in the field. The research projects will be hosted by six different universities and five companies from all over Europe

Liquefied Methane as a Fuel in Swiss Heavy-duty Trucks

The decarbonization of vehicles in the heavy-duty sector is an important contribution to achieving the climate protection targets agreed in Paris. In an interdisciplinary project led by the Bern University of Applied Sciences for Engineering and Informion Technology and the Ostschweizer Fachhochschule, the substitution of conventional diesel fuel with liquefied methane for heavy-duty commercial vehicles is being studied holistically

Verflüssigtes Methan als Kraftstoff im Schweizer Schwerlastverkehr

Die Dekarbonisierung von Fahrzeugen im Schwerlastbereich ist ein wichtiger Beitrag, um die in Paris vereinbarten Klimaschutzziel zu erreichen. In einem interdisziplinären Vorhaben wird unter der Leitung der Berner Fachhochschule für Technik und Informatik und der Ostschweizer Fachhochschule daher die Substitution von konventionellem Dieselkraftstoff durch verflüssigtes Methan für schwere Nutzfahrzeuge in der Schweiz ganzheitlich untersucht

Combining Heat Pumps with Combistores: Detailed Measurements Reveal Demand for Optimization

AbstractA heating system that combines a ground source heat pump and solar collectors with a combistore was measured in detail in the laboratory by means of “whole system testing”. The test rig thereby emulated a building with floor heating, hot water tappings, flat plate solar thermal collectors and a ground source heat exchanger. The tested heating system covered the heat demand for space heating and domestic hot water preparation in a reliable way with a good annual system performance factor of 4.5 that was determined after the physical test by means of test-calibrated simulation models. Nevertheless the measurements revealed that there is still room for improvements. It was found that the heat pump operates in space heating mode in an oscillating on/off behavior with short runtimes and respectively with a high number of starts and in addition with a supply temperature that is in average 8K above the temperature that is needed in the heat distribution. Furthermore a significant transport of energy, from the upper part of the store that is reserved for domestic hot water preparation to the lower part, reserved for space heating, was detected

Medium temperature solar thermal installation with thermal storage for industrial applications

In 2012, COLAS, the worldwide leader in the bitumen and road coatings sector, has decided to equip one of its regional sites with a solar thermal installation for temperatures up to 200°C. Coupled with a gas boiler, the solar collectors were installed with the dual purpose of meeting the thermal energy needs of a workshop building and to maintain two bitumen storage tanks above its melting point. This article gives a short description of the heating system at this industrial site and of its operating modes. It also describes the numerical model developed for detailed system simulation. First simulation results give a low annual solar heat gain of 94.6 kWh/m2 which is 2.6 times lower than initial estimations. Further investigations will be performed during the ongoing project in order to optimize the solar heat gain and to identify the reasons for this unsatisfactory result

Solar Water Preheating for Open District Heating Nets: CIS Potential

Abstract In heat and power plants with so-called open district heating nets, large quantities of cold water (e.g. 12°C) are heated up to supply temperatures (e.g. 60°C) using fossil fuels. This water, however, can be effectively preheated by uncovered collectors before heating up conventionally to the supply temperature. Due to high basic load, low inlet temperature and good climatic conditions in most parts of the Commonwealth of Independent States (CIS), extraordinary solar gains and very low solar heat costs can be achieved during the frost-free season. The objective of this investigation is to identify heat and power plants in the CIS which are appropriate for solar water preheating. For this purpose, large (or central as it is called in the CIS) operated heat and power plants were identified and evaluated. It was found that 38 out of 197 heat and power plants are in principle appropriate for this kind of solar thermal technology. In addition, this study includes an economic analysis of the technology based on previous experimental and theoretical results. Solar heat costs of less than 0.01 €/kWh th and a payback time of about 9 years are expected