The latest solar development in Latvia. Claudio ... University and Lund Institute of Technology, as well as ... barriers to solar energy use in Latvia were identified.
European Nordic Energy Research cooperation on solar combisystems. The latest solar development in Latvia Claudio Rochas Department of Energy Systems and Environment, Riga Technical University Riga, LV1010, Latvia and Dagnija Blumberga Department of Energy Systems and Environment, Riga Technical University Riga, LV1010, Latvia
ABSTRACT This paper presents an ongoing research project on solar combisystems for the Nordic and Baltic countries of Europe. The aim of the project is to develop competitive solar heating systems, which are attractive to buyers and to educate experts in the solar heating field. The participants of the project, which is financed by Nordic Energy Research and the participants themselves, are the universities: Technical University of Denmark, Dalarna University, University of Oslo, Riga Technical University and Lund Institute of Technology, as well as the companies: Metro Therm A/S (Denmark), Velux A/S (Denmark), Solentek AB (Sweden), SolarNor (Norway) and SIA Grandeg (Latvia). In Denmark and Norway the research and development focus is on solar heating/natural gas systems and in Sweden and Latvia the focus is on solar heating/pellet systems. Additionally, Lund Institute of Technology and University of Oslo are studying solar collectors of various types being integrated into the building. The paper focuses on the Latvian situation. Different barriers to solar energy use in Latvia were identified during the inception phase as well as the market potential for solar combisystem. The paper illustrates the most significant activities that were carried out until now in Latvia, in particular the development of a new biomass-solar laboratory and the developed prototype of solar combisystem, which will be installed in different a demonstration projects. Keywords: solar combisystem, barrier to solar energy development, compact system concept, system optimization.
INTRODUCTION In Denmark, Sweden, Norway and Latvia respectively 25%, 23%, 27% and 35% of the country’s total yearly energy consumption is used for heating of buildings, while the yearly solar radiation on the horizontal surface of the country is respectively 180, 1030, 1200 and 3130 times greater than the country’s total yearly energy
consumption. Certainly, the potential for solar heating systems is large, even at Northern latitudes [1]. Energy efficiency projects and renewable energy projects are gaining popularity, not only in Latvia, but also in all the postsocialist countries. A great number of projects are implemented within international co-operation frameworks. These projects are part of national energy policy where, regarding the use of energy resources, the most important issues are: How to increase of the share of renewable energy sources; How to rationalise the use of energy resources, i.e. increase the energy efficiency at all levels of the energy systems (production, distribution and end use). During the past 15 years since regaining independence, more than 15 different national programmes and policy strategy documents have been developed in Latvia concerning both issues. Particularly significant are The National Renewable Energy Program (2000), the National Energy Efficiency Strategy (2000) and the National Allocation Plan (2004). However, all these program did not seriusly address the potential of solar energy in the country – leading to a situation where solar thermal market is practically not exsisitng and the number of installed solar heating systems is very small for a total collector area of about 200m2 only, which were installed in framework of support programs. As well as in Northern Europe countries, in the last 10 years the market for solar heating systems has not been as good as in the central European countries, like Austria and Germany, where major companies are now active in the market. Other significant factors have characterized this situation in Latvia: the lack of information and awareness on solar systems, lack of players in the market (industry, sellers, installers, consultants, etc…), and the fact that the cost of solar heating is perceived by the final customer to be relatively high compared to the price of other more traditional heating systems. District heating (DH) is the most common energy form for heating houses in high density cities of Latvia, while single family houses not connected to the DH grid are typically headed by natural gas, liquid petroleum gas (LPG), wood logs or pellets. Electricity for heating is as well as used in some case. There are two ways to reduce the energy costs of solar heating systems. One is based on rationalisation effects due to
large-scale production of solar system components. This way is only possible if there is a continuous sufficient demand for solar heating systems. The alternative is to improve the performance/cost ratio of the solar heating systems by means of development of improved systems [1]. Recent studies within Task 26 of the International Energy Agency’s Solar Heating and Cooling Programme have shown that significant improvements can be made to solar heating systems, and a few German and Austrian companies have already optimised their systems [2]. These optimized systems are complete systems including boiler as well as solar collectors, and are often installed in new buildings or when an existing boiler is being replaced. However, these systems are not readily available in the Nordic countries. Therefore it has been decided to use the knowledge gained from this previous international collaboration in connection with development of solar heating systems for North European countries.
RESEARCH PROJECT: COMPETITIVE SOLAR HEATING SYSTEMS FOR RESIDENTIAL BUILDINGS During the period 2003-2006, the research project “Competitive solar heating systems for residential buildings” (REBUS) will be carried out in cooperation between leading research institutes and companies in the solar heating field in the Nordic and Baltic countries. The aim of the project is to develop solar heating systems, which are attractive to buyers. Up to 50% of the energy consumption in the building could be covered by solar energy; conventional energy resources will cover the remaining energy consumption. Solar heating for new buildings as well as for retrofits has been addressed. The project includes education, research, development and demonstration. The participants of the project, which is financed by Nordic Energy Research and the participants themselves, are the universities: Technical University of Denmark (DTU), Dalarna University (Sweden), University of Oslo (Norway), Riga Technical University (RTU, Latvia) and Lund Institute of Technology (Sweden) as well as the companies Metro Therm A/S and Velux A/S from Denmark, Solentek AB from Sweden and SolarNor from Norway, Grandeg from Latvia. The project consists of a number of Ph.D. studies in Denmark, Sweden and Latvia and a post-doc. study in Norway. Close cooperation between the researchers and the industry partners ensures that the results of the project can be utilized. By the end of the project the industry partners will be able to bring the developed systems onto the market. In Denmark and Norway the focus is on solar heating/natural gas systems, and in Sweden and Latvia the focus is on solar heating/pellet systems. Further, Lund Institute of Technology and University of Oslo are studying building integrated solar collectors of various types.
RELATED ACTIVITIES OF THE RESEARCH PROJECT During the first part of the Ph.D. projects, two Ph.D. courses on solar energy have been organized at Technical University of Denmark and Riga Technical University, with participants from all around the world. During the courses, which included lectures by experienced researchers, visits to manufacturers and solar heating systems as well as social arrangements, the students worked on different topics within the solar energy field with the aim to prepare state of the art reports. The students presented their findings and their Ph.D. projects to the other participants of the courses. Valuable networks among the Ph.D. students and the teachers were established. A third specialized Ph.D. course focusing on thermal stratification in solar storage tanks will be organized at Technical University of Denmark in September-October 2005. The Ph.D. students of the project have carried out/will carry out study stays at one of the other participating universities for a period of about 6 months. In this way good cooperation between the participating universities is ensured. In the framework of this project in RTU has been developed a new solar-biomass laboratory were it is possible to test and develop new prototypes of solar domestic hot water systems and solar combisystem. The Laboratory includes hydraulic loops for simulation of space heating load and solar energy gain. The Laboratory is equipped with spectrometers, gas analyzers, data loggers and set of different sensors for detailed analysis and system optimization. A full-equipped section has been developed for assembly and modification of prototypes and hydraulic loops.
BARRIERS TO SOLAR ENERGY IN LATVIA AND MARKET POTENTIAL One of the activities implemented under the REBUS project has been a market survey concerning solar combisystem in Latvia. In particular the study addresses new and retrofitted single-family houses. The survey included interviews to the following target groups: Investors (like banks or private investors), Designers, Real estate companies, Construction companies, Architects. The survey included different aspects and in particular tried to understand barriers and which solar combisystem is more suitable for the Latvian market and its market potential. One of the main barriers identified during this survey has been the lack of information on solar thermal systems. Even the interviewed architect group, which is daily working with design aspects of buildings, was not too aware of the possibility of using solar collector elements for modern design of single family houses. All groups were often uncertain on the general questions on solar energy technology, on its perspective.
All the respondents agreed that today the investment costs for solar thermal system are too high for making them competitive with more traditional heating system. However, often the respondents were uncertain, or did not know exactly the range of investment needed for a solar combisystem. From this survey another barrier arisen from the answers of the interviewed, seems to be a lack of general governmental support to renewable energy sources. In particular the fact that in Latvia have never been proposed support scheme to households for using new and efficient technologies in their houses. Finally, it was recognized that it will be as well as very important to have local demonstration projects, because they would help to convince eventually interested clients. Today in Latvian there are only few cases of use of solar combisystems in single family houses – therefore under this point of view is possible to argue that the technical potential for this type of project is high; even because in the last years the real estate sector has had a very strong development. Some of the questions of this survey were addressed to understand which combisystems could be successfully introduced in Latvia – or at least which characterizing the systems should have. In general the buyer of single-family houses pay attention to the heating system of their new house. From one side they often would like to have a natural gas boiler or even some case it was are asking for district heating. These solutions are very appreciated for the very high degree of automation and for the small space area taken in the house. From the other side it was possible to see that the clients of single-family houses are willing and would like to use wood based fuels; in some case for aesthetical reasons – and the wish to have a visible and cosy heat source in the leaving room and in some other case because of the possibility to use cheaper fuels compared to fossil fuels solutions. In the new building (built in the last 5-7years), the general wish is to assign a very small area to the heating system, and generally never more than 4m2. Different is the situation in existing and older building, where in some cases there is dedicated room for the heating system. From this survey was possible to conclude that two combisystem concepts could be successfully introduced in Latvia: a system taking small space area (very good possibility would be a 60x60x200cm cabinet concept) and with a good degree of automation; in particular this solution could be introduced in the development of new housing project, involving investors, develops and architects. This solution could be as well as attractive for the owners of single family houses, who have small space area for the heating system and requires an high degree of automation, given the barriers above mentioned are mitigated. a simpler system, to be installed in a boiler room and with separate components, where a high degree of automation is not essential.
Concerning the auxiliary heating sources, it seems that the main alternative would be natural gas (where available) and then wood base fuels, like wood pellets or wood logs.
DEVELOPMENT OF SOLAR HEATING SYSTEMS System concept The basic idea was to develop a concept that could be very easily installed, taking small space area in the building and which would has a nice outlook. Several system concepts with different store, boiler, space and hot water preparation methods have been proposed and simulated at DTU in the beginning of the project. Beside the thermal performance and system efficiency mainly the production costs of the store and the compactness of the system in order to integrate it into a 60x60 dimension proved to be the decisive points for the choice of the concept. Also the possibility to integrate a gas or pellet boiler as auxiliary heat source was important for the decision. The final developed concept system consists of a highly prefabricated technical unit with all the equipment of the systems including the natural gas/pellet boiler and one or more units with the heat storage. The units are built into 60x60 cm cabinets (see Figure 1). The integration allows faster installation and reliable systems. Although the system is highly prefabricated, there is significant flexibility: choice of gas or pellet boiler; choice of system size, with larger systems either having multiple 60 x 60 cm cabinet stores, or single larger stores. Two main solution of the concept have been proposed; the first solution with only one solar store and the second with two stores: the solar store and a smaller standby volume store in the technical unit. The one store solution is suitable for the use with a gas boiler that can directly provide enough heat to cover the highest hot water demand (30-35 kW) and is also fast enough to provide the power within few seconds.
Figure 1. system concept of the REBUS project developet at DTU and Dalarna University.
For smaller, simpler and less expensive gas boilers with a power below 30 kW and for pellet boilers a second store is
necessary. This store contains a standby volume that when heated can provide the peak power demand for domestic hot water. The size of the standby store depends on the size of the boiler and the time delay until the boiler can provide heat with a certain set temperature. Concerning the solar tank, the final concept is based on a simple buffer tank with pipe in- and outlets inserted from the bottom of the tank as already produced by Metro Therm. The solar circuit and the hot water preparation are connected to the tank by external flat plate heat exchangers. The space heating and hot water are prepared in parallel with the same speed controlled circulation pump using heat from different levels of the tank. In order to keep a good stratification the return flow from the domestic water heat exchanger and space heating is supplied to two different levels of the tank depending on the return temperature [3]. The goal is, by the end of the project, to have natural gas/solar heating system units and pellet/solar heating systems installed in several houses for field tests.
DEMONSTRATION SYSTEM IN LATVIA A number of solar combisystems based on the developed solar heating systems and components will be built in one family houses in the autumn of 2006. In particular one system will be installed in Denmark, one in Sweden and one in Latvia. The systems will be equipped with monitoring systems in such a way that the thermal performance and energy savings of the systems can be determined. For instance, Latvia solar heating will be installed in a one family house with an existing natural gas boiler. The energy demand as well as the natural gas consumption has been measured since September 2005. It is therefore possible to determine the energy savings of the solar heating system based on measurements from the house without and with the solar heating system installed. The measurement periods for the demonstration systems will be about 1 year.
FUTURE WORK The system concept will be modeled and simulated with the dynamic simulation tool TRNSYS [4] to evaluate the thermal performance of the systems. Parameter and detailed design studies will be performed and calculated results will be compared to the prototype measurements in order to validate the simulation model and the validated model will then be used to optimize the system design. Performance data will also be obtained from the measurements at the demonstration sites. It is planned to produce a second generation of prototype, further simplified in order to reduce production costs but keeping good level of efficiency and flexibility. In particular further test will be used implemented on the controller and controller software.
ACKNOWLEDGEMENT We are grateful to the Nordic Energy Research for their financial support for this work within the REBUS project. A particular thanks to Alexander Thür - PhD student at Technical University of Denmark - and Frank Fiedler – Phd. student of SERC (Solar Energy Research Center) at Dalarna University – for the development of the prototypes and system concepts.
REFERENCES [1] S. Furbo, et. al. Competitive solar heating systems for residential buildings, NorthSun2005, 10th International Conference on Solar Energy at High Latitudes. Vilnius, Lithuania. May 25-27, 2005. [2] W. Weiss, Solar Heating Systems for Houses, a design handbook for solar combisystems. [3] F. Fiedler, C. Bales, The actual status of the development of a Danish/Swedish system concept for a solar combisystem, NorthSun2005, 10th International Conference on Solar Energy at High Latitudes. Vilnius, Lithuania. May 25-27, 2005. [4] Klein, S., et al. (2004) TRNSYS 16.0 Transient Simulation Program, SEL, University of Winsconsin, Madison, WI, USA.
