Jan-Olof Dalenbäck

Evaluation of storage configurations with internal heat exchangers

An international standard, ISO/DP 9459-4A, 1996 has been proposed to establish a uniform standard of quality for small solar heating systems. In this proposal, system components are tested separate ...

Large-Scale Solar Heating and Cooling Systems in Europe

In total, there are about 19 million m2 of glazed solar collectors in Europe, corresponding to about 13,5 GWth, where the majority of the collectors are installed in small systems with up to a few kWth. However, the relevant heat loads vary from a few kWth up to several GWth and about 9% of the heating loads in Europe are covered by block and district heating systems. So far, only a minor part of the European collector market comprises large-scale applications. European large-scale solar heating plants having more than 500 m2 (~350 kWth) of solar collectors have only about 140 MWth altogether, i.e. about 1% of the present installations in Europe. There is thus a need to develop large-scale applications in order to utilize the full potential of solar heat to cover existing heat loads. The first large-scale solar heating applications were introduced in Sweden in the late 70’s. Interests in large-scale solar heating, especially in Germany and Austria, increased during the 90’s and about 100 plants with more than 500 m² of solar collectors are put into operation since mid 90’s. Large-scale plants show more favourable costs of solar heat than most small systems and a strong market growth for small systems in Spain and France could now lead to an increased interest for large-scale applications also in Southern Europe. However, Sweden is still the leading country with 22 out of about 120 European large-scale plants (>500 m2; >350 kWth) in operation. The majority of large-scale solar applications are installed in block and district heating systems, but there are now also an increasing number of solar cooling plants. The paper gives an update on the present status and describes initial visions and strategies to increase the development of large-scale solar thermal applications within the European Solar Thermal Technology Platform (ESTTP) in co-operation with representatives for Euroheat & Power.

SWEDISH SOLAR HEATING WITH SEASONAL STORAGE - DESIGN STUDIES

ABSTRACT This paper summerises the Swedish research program for solar heating systems with seasonal heat stores. Existing plants are described together with the background to new plants, the designs and ratings of which are directly based on experience from and research related to, the existing plants. Based on present-day knowledge, these solar heating systems should be designed and rated to provide an energy coverage of about 70–80 % of the heat requirement of the load. They should be realized using flat plate collectors in large moduls, with a basically simple design incorporating separate heat storage and discharge circuits.

Simulation of Energy Used for Vehicle Interior Climate

In recent years fuel consumption of passenger vehicles has received increasing attention by customers, the automotive industry, regulatory agencies and academia. However, some areas which affect the fuel consumption have received relatively small interest. One of these areas is the total energy used for vehicle interior climate which can have a large effect on real-world fuel consumption. Although there are several methods described in the literature for analyzing fuel consumption for parts of the climate control system, especially the Air-Condition (AC) system, the total fuel consumption including the vehicle interior climate has often been ignored, both in complete vehicle testing and simulation. The purpose of this research was to develop a model that predicts the total energy use for the vehicle interior climate. To predict the total energy use the model included sub models of the passenger compartment, the air-handling unit, the AC, the engine cooling system and the engine. Verification of the model was carried out against several complete vehicle tests using the new European driving cycle (NEDC) with different ambient temperatures ranging from −18°C to 43°C, different thermal states such as heat up or steady state and different sun loads. The agreement between simulation and measurement was demonstrated to be good for all compared properties except the compressor mechanical load. This research shows that it is possible to create a model that predicts the total energy use for vehicle interior climate for a wide range of different conditions.

Measurements of Energy Used for Vehicle Interior Climate

Fuel consumption of vehicles has received increased attention in recent years; however one neglected area that can have a large effect on this is the energy usage for the interior climate. This study aims to investigate the energy usage for the interior climate for different conditions by measurements on a complete vehicle. Twelve different NEDC tests in different temperatures and thermal states of the vehicle were completed in a climatic wind tunnel. Furthermore one temperature sweep from 43° to–18°C was also performed. The measurements focused on the heat flow of the air, from its sources, to its sink, i.e. compartment. In addition the electrical and mechanical loads of the climate system were included. The different sources of heating and cooling were, for the tested powertrain, waste heat from the engine, a fuel operated heater, heat pickup of the air, evaporator cooling and cooling from recirculation. It was found that a separation of the sources and sink was possible and increased the understanding of the energy usage. Further the study showed that the sources were very dependent on the powertrain and that ambient conditions and thermal state of the vehicle, i.e. thermal load, had a very large impact on the needed energy.

Reduction of Energy Used for Vehicle Interior Climate

In recent years fuel consumption of passenger vehicles has received increasing attention by customers, the automotive industry, regulatory agencies and academia. However, some areas which affect the fuel consumption have received relatively small interest. One of these areas is the total energy used for vehicle interior climate which can have a large effect on real-world fuel consumption. Realistic combinations of energy saving measures were evaluated regarding the total energy use for vehicle interior climate using a one dimensional (1D) simulation model. The 1D simulation model included sub models of the passenger compartment, the air-handling unit, the Air Conditioning (AC) system, engine and engine cooling system. A test cycle representative for real-world conditions was developed. The test cycle included tests in cold, intermediate and warm conditions and the results were weighted with the estimated use in each condition. In the investigated case the average electrical power was decreased with 50%, primarily through a new blower control unit. The mechanical compressor power was decreased with 45%, primarily through less engaged AC-system. In addition the energy flow into the passenger compartment, for cooling and heating, was decreased with almost 20%, largely through increased insulation of windows, shell, ducts, and decreased interior mass. All these savings were made without decreasing the potential of thermal comfort for the passengers. When the most beneficial energy saving measures have been implemented further reductions of energy use for the climate control system will become very challenging. To achieve additional energy reductions, with this type of system, the airflow has to be reduced or more energy must be recovered from the air. Many challenges with these measures can be expected.

Simulations of a Solar-Assisted Block Heating System

Two types of simulation software TRNSYS and Polysun are studied to check their suitability for solar district heating system planning. A reference case, a part of the Vallda Heberg district heating system is modelled in both tools and results are compared with available measured data and with each other. Models are successfully calibrated. TRNSYS and Polysun models have deviations in main key figures compared to the reference case less than 2% and less than 8% respectively. A sensitivity analysis of key parameters shows that the two tools give similar results.

A methodology for energy use evaluation in complex buildings - Applied in a shopping mall case study

Appropriate methodologies are needed if energy targets in buildings are to be achieved. Despite the large number of studies concerning sustainable energy use in buildings, few include validation between calculated and measured energy use. It is however well known that there is often a gap between the two. This paper proposes a methodology which aims to more accurately estimate energy use from measured energy, operational data, and technical data, using iterative empirical-theoretical cross-checking. Applying the method provides increased understanding of how uncertainty in input data affects the accuracy of the calculated energy use. A sensitivity analysis is included, which shows what parameters the building is most sensitive to. For these parameters, good input data is important for the calculated results to be correct. Furthermore, these parameters have the largest potential to improve the energy use. The proposed methodology is applied in a case study on a shopping mall in Sweden.

Thermal losses in sealed, gas-filled flat plate solar collectors

A sealed space between absorber and cover glass makes it possible reducing the influence of humidity condensate and dust at the same time as the enclosed space can be filled with a suitable gas for lowering the losses. This paper is about the size of the losses in these collectors. A calculating model of a gas-filled flat plate solar collector was built in Matlab with standard heat transfer formulas. It showed that the total loss can be reduced up to 20% when changing to an inert gas. It is also possible using a much shorter distance and still achieve low losses at the same time as the mechanical stresses in the material is reduced.

SOLAR DHW SYSTEM EVALUATION WITH F-CHART

ABSTRACT Several solar heating systems with roof-integrated collectors have been installed in multifamily houses during the last five years in Sweden. The outstanding features of the systems are the flexibility and the large amount of conventional heating technology in the system design. Measured performance agrees with F-Chart calculations, and F-Chart could thus be used to estimate the performance of these systems in different locations. The performance for DHW systems in Goteborg, Sweden and Madison, U.S. are shown as an example.