Resources and Research
The built environment influences and impacts on the natural environment in many ways. The magnitude of these influences can be reduced through thoughtful design, the adoption of appropriate technologies, and by changing the way we use the earth’s resources.
In achieving this, the Department of Public Works has conducted a number of research projects that specifically focus on emerging relating to the built environment’s impact on the natural environment. This research ranges from improving efficiency of glasshouses to hybrid air conditioning.
In addition, a range of guidelines and educational resources have been produced to assist other government departments and the general public on understanding and reducing the impacts of the built environment.
The Energy Efficient Glasshouse Research Project
Introduction
Crops planted outdoors generally have one growing season per year. This can be unacceptable for research purposes, as the time required to produce any results can be excessive.
To overcome this problem, research crops are grown in glasshouses, where two, three and sometimes four crop rotations per year can be obtained, reducing research time considerably. The construction of these glasshouses has normally been based on types used in Europe i.e. single-skin glass and usually built with a north-south orientation.
With these conventional glasshouse structures, the growing of winter crops in summer or the growing of summer crops in winter requires the cooling or heating of the glasshouse respectively.
Energy utilisation indices for conventional glasshouses range from 2,000 to
2,500 Mj/m2/year compared with office buildings that have a range from 630 to 1,110 Mj/m2/year. With such large energy requirements, any improvements in energy efficiency and sustainability will have a larger impact than would a corresponding change in a standard office building.
Conventional glasshouses are heated with either oil-fired space heaters or various forms of electrical heating systems (using grid-supplied electricity). As a consequence of the exorbitant heating costs involved, the volume of crops grown using glasshouses is constrained, as is the period over which cultivation takes place.
A joint research project between Technical Services, Department of Public Works and the then Department of Primary Industries and Fisheries has lead to the development of a unique energy-efficient and economical agricultural greenhouse design.
Under this collaborative research arrangement engineers in Technical Services developed full-size energy-efficient greenhouses that are now in use at two research centres operated by the Department of Environment and Resource Management in Southeast Queensland.
The first generation of the Solar Greenhouse was built at the Hermitage Research Station near Warwick in 1995. This greenhouse was designed for the growing of summer crops on a year-round basis, and utilised solar-heating applications to maintain temperatures over the winter period.
In trials against the performance of a conventional glasshouse for the growing of sorghum, the growth rates and pollen production in the Solar Greenhouse were such that the research cycle has been reduced from four years to three years.
With the success of the first generation of Solar Greenhouse, when a new glasshouse was required for the then Department of Primary Industries’ Leslie Research Centre in Toowoomba, the decision was taken to develop a second generation of the Solar Greenhouse concept and extend its use to both summer and winter crops.
The challenge was to find ways of adapting energy-efficient cooling technologies to allow wheat to be grown in the glasshouse during summer. Cheaper summer cooling is a challenge that has worldwide implications for intensive horticulture in the sub-tropics and tropics.
The Biotechnology Solar Greenhouse is enabling researchers to develop superior wheat varieties on a continuous growing cycle. With Australia’s wheat export market worth more than $6 billion per year, the outcomes of this program will be improved varieties offering higher yields, greater tolerance of drier areas, and improved resistance to disease and insect attack. The speeding up of the wheat-breeding program being carried out at the Leslie Centre is enabling new varieties to be delivered to growers up to five years earlier than would otherwise be the case.
This innovative greenhouse, commonly referred to as the Solar Greenhouse and commissioned in 2001, is a unique concept featuring low-cost materials, natural ventilation and passive systems, coupled with solar-powered evaporative coolers to maintain temperatures and conditions within the desired range for plant breeding and growth throughout the year. The solar greenhouse is a 168m2 facility that is able to maintain temperatures between 15°C and 25°C using winter heating and summer cooling while using virtually no grid-supplied electricity or other non-renewable forms of energy. Savings of more than AU$12,000 per year on electricity costs have been reported.
Biotechnology Solar Greenhouse, Leslie Centre - Toowoomba
In order to meet the needs of the then Department of Primary Industries and Fisheries, engineers in Technical Services of the Department of Public Works devised new concepts in both construction and system operation.
The Biotechnology Solar Greenhouse at the Leslie Centre is an energy-efficient 168m2 facility divided into three bays. The dry bulb temperature for each bay is individually controllable within the range of +18ºC to +25ºC.
The second-generation Solar Greenhouse design employs the technologies used in the Hermitage facility to address winter heating needs coupled with solar-powered evaporative coolers to control summer temperatures. The Solar Greenhouse utilises leading edge applications of passive systems for energy management and the inducement of natural ventilation in association with solar-powered cooling to provide optimum plant growing conditions. The concept maximises the use of natural light, solar energy and passive systems to eliminate the need for grid-supplied electricity to provide cooling and heating.
Economics and Energy Efficiency
The application of passive design principles resulted in a glasshouse shape for which the cost of the structure was approximately two-thirds that of a conventional glasshouse of equivalent size. The cost savings achieved relative to the structure more than offset the cost of providing the renewable energy based electrical energy supply and the direct current drive motors.
A typical glasshouse of conventional design and of similar area will consume upwards of 336,000MJ of energy over one year’s operation. Assuming an electricity charge of 10c/unit (kWh), a typical annual cost for electricity consumption is upwards of AU$9,280.
In comparison, actual electricity costs for the Biotechnology Solar Glasshouse are AU$62.33 per year – of which $60 is electricity used by the computer system and $2.30 (at 10 cents per kWh) is used in running the motors that operate the variable air vents. This saving in the use of grid-supplied electricity represents a reduction of some 86 tonnes of CO2 emissions per year.
A further benefit is that not only is the Solar Greenhouse cheaper to build, its economic lifetime is assessed as being at least 50 years, compared with that of the conventional glasshouse which is typically 30 years.
The Leslie Centre’s Biotechnology Solar Greenhouse was commissioned in February 2001 and has been performing above design expectations. The Solar Greenhouse has enabled the Centre to significantly speed up its wheat breeding program by producing a true breeding variety in one generation instead of having to wait five or six generations. This has a significant impact on the economics and efficiency of the Centre’s plant breeding program.
- Higher light levels & effective diffusion for better plant illumination
- Hail resistant skin
- Induced natural ventilation
- Photovoltaic (solar) cells
- Solar-powered, variable evaporative coolers
The Future
The Solar Greenhouse concept offers substantial benefits to the horticultural industry. However the technologies utilised in the Solar Greenhouse have a wider application than for this type of building alone. These technologies can also be utilised to satisfy comfort criteria for smaller enclosed-space facilities such as schools, research facilities, and residences, with a minimum input of energy. The performance data from the existing Solar Greenhouses is now being used by Technical Services Division to develop similar systems for the residential and school building sectors.
The two-minute video features breakthroughs in solar greenhouse design, devised by the Technical Services Division within the Department of Public Works in conjunction with the then Department of Primary Industries and Fisheries.
Note: To take a tour of the glasshouses, click on the links below. You require either a Quicktime plug-in or Windows media player.
- Click here to view Warwick glasshouse 4.7m Quicktime
- Click here to view Warwick glasshouse 4.7m Windows Media player
- Click here to view Toowoomba glasshouse 5.5m Quicktime
- Click here to view Toowoomba glasshouse5.2m Windows media player
Last Updated 05/08/2009
