Solar heating systems for recirculation aquaculture

The literature over the past 25 years indicates that there has been a continued interest in using passive and active solar technologies to reduce the conventional energy required to maintain water temperatures in small recirculation aquaculture systems. Although all of the experimental systems reviewed report favourable results, there is little information available to guide system designers. This paper describes the use of a simulation model to predict the annual conventional energy consumption of a 10.6 m3 RAS enclosed in a double layer polyethylene greenhouse in two different climates. The water was maintained at 22.5 °C and the recirculation rate was 10% of tank volume per day. Simple unglazed solar collectors have also been combined with the greenhouse to further reduce energy consumption. The effect of increasing collector area on the solar fraction and utilization of useful energy was predicted. Finally, the model was used to investigate the relationship between the occurrence of condensation on the inner cover, ventilation rates and energy use. It was found that in a hot dry climate, the greenhouse alone was sufficient to reduce the conventional energy requirements by 87%; while in the cooler temperate climate reductions of 66% were possible. When solar collectors were added to the system, conventional energy requirements were reduced further and depended on the area of collector used. For example, in the temperate climate location, conventional energy requirements were reduced to 23% of a RAS enclosed in a non-solar building when 26 m2 of solar collector inclined at the optimum angle for winter energy collection were used. Although condensation could be successfully reduced by ventilation of the greenhouse, this increased conventional energy requirements because the potential for evaporation was increased. Covering the tanks at night was found to be a more effective strategy because it reduced condensation and conventional energy use simultaneously.

Solar heating for commercial swimming pools – experiences in south-eastern Australia

Commercial swimming pools, particularly aquatic centres are increasingly common features of large towns and cities in Australia as people are encouraged to increase their levels of physical activity. Swimming is regarded as a low impact form of exercise and use of indoor facilities allows this to continue all-year round. Aquatic centres are large users of energy for water and space heating with an energy intensity which can be up to seven times that of a commercial office building in Australia. Much of the energy is used to heat water to relatively low temperatures and therefore solar energy technology is capable of providing this energy. In the residential sector, solar thermal systems for heating water and swimming pools is well-established. This is not the case for commercial swimming pools i.e. aquatic centres. In Victoria, a program to encourage commercial pool operators to install solar systems was funded in the early 1980s. This paper describes an investigation into the current use of and attitudes to solar systems in commercial pools through a survey of municipal pool operators in Victoria, south-eastern Australia. The survey found that there has been very little increase in the use of solar energy and that barriers to the use of the technology remain the same as they were nearly 30 years ago. Lack of roof area, poor payback periods and an inability of solar to meet pool heating needs are the most common misconceptions. To improve the uptake of solar heating in commercial pools, further research, particularly looking at the feasibility of integrating traditional heat sources with solar collectors using smart control, is required. An incentive programme and the education of the new generation of consultants and aquatic centre operators, unfamiliar with the potential benefits of solar systems, would also help to increase their uptake.

Seasonal storage for solar thermal systems in Australia?

Seasonal storage systems have been operating in various European countries since 1985. Combined with solar collectors, these systems are known as ‘central solar heating plants with seasonal storage’ (CSHPSS). While these systems have been shown to be technically feasible, their cost is still too high to make them competitive with fossil fuels.

In Australia, we have quite different conditions to those countries where CSHPSS have been trialled. In general, we experience higher radiation levels, ambient temperatures and cooling loads. Our heating loads and energy prices are also usually lower. As a result, any evaluation of CSPSS operating in a European context may not be valid for Australian conditions. To the authors’ knowledge, no evaluation of these systems has been carried out for Australia.

This paper therefore attempts an initial assessment of these systems and their viability for Australia. The paper first describes the various types of CSHPSS and then reviews their current status. The performance of one type of CSHPSS operating in several locations of Australia has been predicted using a TRNSYS model. The simulations indicated that the design guidelines for Europe are inappropriate for Australia and would result in greatly over-sized systems.

An indication of the financial viability of the system was determined by calculating a simple payback period for a variety of fossil fuels. This type of seasonal storage systems appears to be financially attractive in areas of southern Australia where the solar system is displacing LPG.

Solar thermal aided power generation

Fossil fuel based power generation is and will still be the back bone of our world economy, albeit such form of power generation significantly contributes to global CO2 emissions. Solar energy is a clean, environmental friendly energy source for power generation, however solar photovoltaic electricity generation is not practical for large commercial scales due to its cost and high-tech nature. Solar thermal is another way to use solar energy to generate power. Many attempts to establish solar (solo) thermal power stations have been practiced all over the world. Although there are some advantages in solo solar thermal power systems, the efficiencies and costs of these systems are not so attractive. Alternately by modifying, if possible, the existing coal-fired power stations to generate green sustainable power, a much more efficient means of power generation can be reached. This paper presents the concept of solar aided power generation in conventional coal-fired power stations, i.e., integrating solar (thermal) energy into conventional fossil fuelled power generation cycles (termed as solar aided thermal power). The solar aided power generation (SAPG) concept has technically been derived to use the strong points of the two technologies (traditional regenerative Rankine cycle with relatively higher efficiency and solar heating at relatively low temperature range). The SAPG does not only contribute to increase the efficiencies of the conventional power station and reduce its emission of the greenhouse gases, but also provides a better way to use solar heat to generate the power. This paper presents the advantages of the SAPG at conceptual level.

A scale-model room as a practical teaching experiment

A practical experiment is described which was used to help university students increase their understanding of the effect of construction methods and window design on passive solar heating and electrical heating. A number of one tenth scale model rooms were constructed by students and sited out-of-doors in the late autumn. The models were fabricated to mimic available commercial construction techniques with careful consideration being given to window size and placement for solar access. Each model had a thermostatically controlled electric heating element. The temperatures and electricity use of the models were recorded using data-loggers over a two week period. The performances of the models based on energy consumption and internal temperature were compared with each other and with predictions based upon thermal mass and R-values. Examples of questions used by students to facilitate this process are included. The effect of scaling on thermal properties was analysed using Buckingham’s p-theorem.

A typical meteorological year for energy simulations in Hamilton, New Zealand

Typical Meteorological Year (TMY) data is used extensively in building energy simulations and solar energy analysis. TMY data for New Zealand, however, is relatively limited and no such data existed for Hamilton. Ten years of hourly meteorological data was analysed, and a TMY was developed. Simulations using the TMY data were conducted to determine the performance of a solar pool-heating system. It was found that the TMY was able to predict the annual performance of this system to within 2% of the long-term mean. It is intended that this TMY could be used to perform simulations on building energy use and solar heating systems in Hamilton.

Solar industrial process heating in Australia - Past and current status

Thirty years ago in Australia, there was a significant research, development and demonstration programme in solar industrial process heating (SIPH). This activity was led principally by the Commonwealth Science and Industrial Research Organisation, the country’s main scientific research body. Other state government bodies also funded demonstration projects. Today, there is very little SIPH activity at any level in Australia. The contrast with the progress in other renewable energy technologies like wind and solar photovoltaic systems is striking. While the implementation of these technologies has progressed, SIPH has gone backwards. If Australia is to decarbonise its economy at the rate required, a massive deployment of solar thermal technology in those industries which use large quantities of low temperature hot water is also required. Recent developments nationally and internationally may rekindle new applications of solar thermal energy use by industry. This paper reviews the past achievements in SIPH in Australia and describes the lessons learned in order to better prepare for any new wave of SIPH activity.

Performance of a 120 m2 solar air heater for a commercial building in Victoria

The operation of two 60 m² solar air heaters serving a large studio teaching space has been monitored for a twelve month period. The solar contribution of the heaters was found to be less than 5%, and in some instances the heaters actually contributed to the space heating load. A validated mathematical model of the studio and it’s heating, ventilation and air conditioning system was used to investigate performance improvement strategies. It was found a different control strategy and recommissioned control sensors would substantially improve the solar air heater performance.

The effect of colour on the thermal performance of building integrated solar collectors

The use of solar collectors with coloured absorbers for water heating is an area of particular interest when considering their integration with buildings. By matching the absorber colour with that of the roof or façade of the building, it is possible to achieve an architecturally and visually pleasing result. Despite the potential for the use of coloured absorbers, very little work has been undertaken in the field.

In this study, the thermal performance of a series of coloured (ranging from white to black), building integrated solar collectors for water heating was examined both theoretically and experimentally. Subsequently, the annual solar fraction for typical water heating systems with coloured absorbers was calculated. The results showed that coloured solar collector absorbers can make noticeable contributions to heating loads. Furthermore, although their thermal efficiency is lower than highly developed selective coating absorbers, they offer the advantage of improved aesthetic integration with buildings.

Solar energy use for energy savings in dairy processing plants

New Zealand is one of the world’s largest producers of dairy products and has a climate with high levels of solar radiation; however, the use of solar energy in the dairy processing industry has received limited attention. An examination of historical records found that the annual peak in New Zealand milk production and processing occurs at a time when solar radiation levels are increasing markedly. An F-Chart analysis was used to simulate the performance of large-area arrays of solar collectors and to determine their suitability for heating and cooling in a dairy processing environment. For the study four types of solar collectors were analysed: glazed flat plates, evacuated tubes, evacuated tubes with CPC reflectors and a building-integrated solar collector under development at the University of Waikato (UoW). It was found that of these echnologies, both flat plate and evacuated tubes with CPC reflectors could make useful heating and cooling contributions. Furthermore, the solar fraction was determined mainly by the collector area to storage volume ratio. Finally, it was found that the UoW building-integrated solar collector could make a significant contribution to energy use in dairies and may be an attractive future technology for the industry.

Designing a low cost solar collector system for process industry applications

New Zealand is a large producer and processor of primary products and has a climate with high levels of solar radiation. However, the use of solar energy for heating and cooling in the processing industries has received limited attention.
For this study, the design of a low cost solar collector is analysed and discussed. Furthermore, the methods for integrating the collector into water heating and cooling systems in a hypothetical processing environment are examined. An F-Chart analysis is used to simulate the performance of large-area arrays of the solar collector and to determine its potential contribution to heating and cooling loads.
The study shows that for a storage-based system, the contribution of solar energy is determined mainly by the collector area to storage volume ratio. It is suggested that this low cost collector could make a significant contribution to energy use in processing plants and may be an attractive future technology.

Performance of building integrated solar hot water systems

The integration of solar energy systems into buildings has been the subject of considerable commercial and academic research, particularly building integrated photovoltaics. However, the integration of solar hot water systems into roofing systems has had far less attention. This paper presents the theoretical and experimental results of a novel building integrated solar hot water system developed using existing long run roofing materials.

This work shows that it is possible to achieve effective integration that maintains the aesthetics of the building and also provides useful thermal energy. The results of an unglazed 108m2 swimming pool heater and 8m2 glazed domestic hot water systems are presented.

The experimental results show that the glazed system performs close to the theoretical model and is an effective provider of hot water in certain climates. However it was also found that for larger scale building integrated solar water heating systems, special attention must be paid to the configuration and arrangement of the collectors in order to minimise problems with respect to flow distribution and its effect on collector and system efficiency.