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 technologies, 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

The potential for battery electric vehicles in New Zealand

Several challenges are facing personal transport in New Zealand; the need to reduce carbon emissions, the depletion of cheap oil reserves, increasing congestion, localised pollution and the need for long term sustainability. One possible solution to replace petrol/diesel cars could be the mass deployment of cost competitive, comfortable, attractive, energy efficient battery electric vehicles (BEVs). This paper first discusses the social and technical barriers that have hindered the development of this type of electric vehicle and secondly, how they can now be overcome. The electricity supply for a New Zealand fleet of 2 million battery electric cars is also discussed

Analysis of a photovoltaic/thermal solar collector for building integration

The idea of combining photovoltaic and solar thermal collectors (PVT collectors) to provide electrical and heat energy is not new, however it is an area that has received only limited attention. With concern growing over energy sources and their usage, PVTs have become a focus point of interest in the field of solar energy research. Although PVTs are not as prevalent as solar thermal systems, the integration of photovoltaic and solar thermal collectors into the walls or roofing structure of a building could provide greater opportunity for the use of renewable solar energy technologies in domestic, commercial and industrial applications. As such, the design of a novel building integrated photovoltaic/thermal (BIPVT) solar collector is theoretically analysed through the use of a modified Hottel-Whillier model. The thermal efficiency under a range of conditions was subsequently determined and results showing how key design parameters influence the performance of the BIPVT system are presented

The feasibility of long range battery electric cars in New Zealand

New Zealand transport accounts for over 40% of the carbon emissions with private cars accounting for 25%. In the Ministry of Economic Development's recently released “New Zealand Energy Strategy to 2050”, it proposed the wide scale deployment of electric vehicles as a means of reducing carbon emissions from transport. However, New Zealand's lack of public transport infrastructure and its subsequent reliance on private car use for longer journeys could mean that many existing battery electric vehicles (BEVs) will not have the performance to replace conventionally fuelled cars. As such, this paper discusses the potential for BEVs in New Zealand, with particular reference to the development of the University of Waikato's long-range UltraCommuter BEV. It is shown that to achieve a long range at higher speeds, BEVs should be designed specifically rather than retrofitting existing vehicles to electric. Furthermore, the electrical energy supply for a mixed fleet of 2 million BEVs is discussed and conservatively calculated, along with the number of wind turbines to achieve this. The results show that approximately 1350 MW of wind turbines would be needed to supply the mixed fleet of 2 million BEVs, or 54% of the energy produced from NZ's planned and installed wind farms

An assessment of base load concentrating solar thermal power generation for New Zealand

With increasing pressure being placed on traditional energy sources, both in terms of supply and also regulatory, there is an increasing need to explore alternative generation technologies. In global terms, solar energy has the potential to make a significant contribution to worldwide energy demands in the future. This study examines recent developments in the emerging field of concentrating solar thermal power generation and explores the potential for base load electricity generation using this technology in New Zealand

Performance of a building integrated solar combisystem

Solar combisystems providing both water and space heating to buildings are becoming commonplace in European and North American locations. However, the use of these systems in Australia and New Zealand is still in its infancy. While significant work has been undertaken to characterise the performance of these systems in northern hemisphere locations, this does not necessarily reflect their performance in Australia or New Zealand. This work examines the performance of solar combisystems utilising TRNSYS and F-chart simulations of an integrated solar thermal combisystem installed in a single storey detached dwelling under typical Australian and New Zealand climatic conditions. In doing this, it shows that there is significant scope for increased use of solar combisystems in the cooler climate regions of Australia and New Zealand

Performance of a building integrated collector for solar heating and radiant cooling

Due to their limited temperature range, unglazed solar collectors have long been relegated to providing low cost heating in applications such as swimming pool heating systems. This limited temperature range is due to heat loss: firstly by convection to the surrounding air and secondly by radiant heat transfer to the cold sky. During the day an unglazed collector can be operated as a standard solar absorber to heat water in a storage tank. However, it is possible to take advantage of radiant cooling of unglazed solar collectors by operating them at night. Under night conditions when there is no solar radiation and the sky temperature is low, the collector can radiate heat to the sky and cool a cold storage tank to provide cooling in the building the following day. This study theoretically and experimentally examines the performance of a building integrated collector for heating and cooling and explores the contribution it can make to heating and cooling loads in typical New Zealand and Australian buildings

Experimental performance of water cooled building integrated photovoltaic/thermal solar collectors

The idea of integrating water cooled photovoltaic/thermal collectors into building structures (BIPVT collectors) to provide electrical and heat energy is an area that has received only limited attention. BIPVT collectors are particularly attractive, as the integration of a single photovoltaic and thermal collector into the long-run roofing structure of a building could provide greater opportunity for the use of renewable solar energy technologies. In this study, the thermal efficiency of a novel low cost water cooled building integrated photovoltaic/thermal (BIPVT) solar collector was experimentally measured. The results show that despite being made of a typical roofing material, the thermal efficiency is not unreasonably affected. Furthermore, it is shown that the measured efficiency is similar to that predicted by the Hottel-Whillier equations

Performance of coloured 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, water heating solar collectors is examined. Subsequently, the annual solar fraction for typical water heating systems with coloured absorbers is calculated. The results show 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 sensitive integration with buildings