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EMANZ members will often be asked for advice on the cost effectiveness of alternative forms of renewable energy. This would normally relate to the generation of electricity using wind turbines or photovoltaic (PV) cells however you should not overlook the potential use of renewable sources for the production of heat either in the form of solar hot water or burning biomass or waste. Government policyIn New Zealand over 70% of electricity is generated from renewable sources by harnessing the power stored in rivers, lakes, geothermal fields, wind and biomass. In its latest Draft Energy Strategy, the Government has set an aspirational target to increase the amount of electricity generated from renewable sources to 90% by 2025. The final strategy is expected to be released in mid 2011 but as can be seen from extracts from the draft strategy there is unlikely to be any legislative requirement for or financial assistance to increases in renewable energy in New Zealand. The strategy states: “The Government welcomes and expects to see considerably more investment in renewable electricity generation, particularly from geothermal and wind resources. To support this, the Government will continue to articulate the national benefits of renewable energy in its resource management reform and to remove any unnecessary regulatory barriers. There are good reasons to develop a mix of renewable energy resources, large and small. Developing a diversity of energy resources within New Zealand will significantly contribute to boosting energy security, creating jobs, and increasing the availability of energy to assist economic growth in other sectors. New Zealand will improve its resilience to disruptions in energy supply through utilising a wider range of energy resources and by replacing oil with local energy sources. Additionally, further development and use of renewable resources will help to improve air quality and health, reduce energy-related greenhouse gas emissions and meet the renewable electricity target. Government policies will encourage investment in renewable energy resources, focusing greatest attention on areas where there are particular barriers to investment that Government can overcome, and where economic returns are most likely. Proposed government actions include; Continuing to work with industry associations and councils to remove unnecessary barriers to the uptake of medium and smaller scale renewable technologies. These include those utilising wood, agricultural and landfill residues, solar photovoltaics, solar water heating, air and ground source heat-pumps, and community and smaller scale wind and hydro generation. The Government’s other policies include facilitating development of renewable energy in all forms, including biofuels and direct heating will also assist in lowering emissions.” Electricity generationPresently, when grid supply is available, the cheapest form of electricity will be that supplied through the main grid. The cost of small scale generation from renewable sources cannot compete with the large scale of the main generation companies. While the use of renewable sources of generation can improve the public image of an organisation and be seen as a step towards reducing climate change it is unlikely to reduce costs.For off-grid applications, the most cost effective form of electricity generation is with a micro-hydro system but sufficient volume and head of water are required. Even when the resources are available hydro is often overlooked with PV or wind seen as more ‘sexy’. Solar Hot Water and Heat PumpsAround 1.6% of homeowners in New Zealand have now installed solar water heating systems, and currently there are around 3400 new solar water heating systems installed each year. This number is growing at around 30-40% annually.Although they use electricity, heat pumps are often regarded as a form of renewable energy in that their energy output is greater than the energy input. ECCA has combined these technologies in its solar and heat pump water heating programme. EECA aims to increase uptake of solar water heating and heat pump water heating by:
FundingEECA's efficient water heating programme is designed to get the greatest value for money, by giving the highest grants to those solar water heating systems and heat pump water heaters that save the most energy. It provides grants to eligible systems of $500 or id=mce_marker000, depending on the energy savings offered by the system.
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Photovoltaic (PV)Photovoltaic modules absorb the sun’s energy and convert it into electricity, without emitting noise or producing greenhouse gas emissions. PV is a reliable and proven technology widely used internationally. Technological advances and new forms of PV that are being developed around the world are expected to continue to provide incremental increases in efficiency and reductions in cost. PV is an intermittent generation source. It does not generate electricity at night and is also affected by cloudy weather. New Zealand has good solar resources.PV modules are commonly used in communication systems, water pumps, lights on navigation buoys, and electric fences. While PV is often used in remote areas where connection to the electricity network is difficult or expensive, it is also becoming increasingly popular in urban environments in grid-connected applications. PV modules are generally either mounted on roofs or on the top of purpose-built frames for maximum sun exposure. The modules contain a number of electrically connected solar cells that contain a semiconductor material, usually silicon. Light contains particles called photons. When light hits the solar cells some of the photons are absorbed which frees some of the electrons in the silicon crystal, allowing them to flow through the cell layers to electrical wiring where they create an electrical current. In this regard, PV differs from solar water heating where solar energy directly heats the water. Like other forms of micro-generation, PV has a relatively high upfront cost and, as such, is a long-term investment. PV is not currently price competitive against grid-based electricity without the use of significant subsidies. However, as the technology evolves and manufacturing capacity increases, PV is becoming more affordable. PV is modular, which means you can easily add more modules if you need more power or if your electricity demand grows. Another benefit is that the modules tend to be very robust and require little or no maintenance and are completely silent in operation. Most warranty periods are between 20 and 25 years, although the modules will probably continue to work for up to 30 years. Small wind turbinesWind energy can deliver many benefits: it does not release any greenhouse gas emissions, and the energy source is renewable and local. However, micro-scale wind turbines are costly and wind energy is extremely site specific. You will need to carefully assess the wind at your proposed site, the topography around the site, and the consenting requirements of your local council. While it may seem very windy at your site, it may still not be suitable for a micro wind turbine.Small wind turbines generally have a capacity of 0.3kW - 20kW. Households usually use systems smaller than 5kW, while systems up to 20kW can be used on farms. Wind turbines harness the energy in the wind to generate electricity. The wind turns the rotor blades of the turbine, which then spins a shaft connected to a generator. The generator uses magnetic fields to convert the rotational energy into electricity. Most turbines are horizontal-axis, with the rotor blades mounted upwind of the tower. Tail fins or an active yaw system ensure the blades are constantly facing the wind; however, other designs have the blades downwind of the tower. Turbines should not be sheltered behind trees, buildings, or other obstructions. Disturbed wind flow can reduce the performance of wind turbines in some situations. In urban areas average wind speeds are low and the wind erratic due to building and other obstructions. Turbines create noise, which can be unpopular with neighbours. The wind turbine must be appropriate for the wind resource available at your site and how much electricity you need to generate. For example, a turbine designed to operate at lower speeds could be damaged if regularly exposed to strong winds. Similarly, a turbine designed to operate best in high winds may perform poorly in less exposed areas. Some turbine models will tolerate the constant re-orientation associated with disturbed, turbulent airflows, while other models might wear out sooner under the strain. While wind power can provide renewable electricity at a range of capacities, it is completely dependent on prevailing wind conditions for generation. As such it cannot be relied upon as a sole source of electricity. Diesel generators are used for back up in a number of locations in remote parts of New Zealand, and specific software packages have been designed to manage wind/diesel systems for the smooth production of electricity and also to maximise the renewable energy produced. It is interesting to note that there is increasing interest in using locally produced biodiesel to fuel these generators. Biomass boilersMost sawmills burn wood residues to provide heat for drying timber. The cost of wood residues compared to fossil fuels makes it an attractive source of readily available heat or heat and power. In spite of the growing competition for the residues for other uses, its projected increase in price over the coming years is expected to be less than that for traditional fuels. Although the handling, processing and combustion of the residues may involve a higher capital outlay it an economically attractive fuel source. As sawmills usually have surplus wood residues on site, this can cost effectively be used to produce heat and power energy.There is now growing use of wood fuel for boilers in other applications. EECA supports the development of the wood energy sector by providing advice and support on both the supply and demand side. In the past, EECA has provided funding for a number of wood energy demonstration projects. However they are now focusing on sharing the findings of these projects and are no longer offering funding for wood energy grants. The EECA programme has helped raise awareness in the use of wood fuel and many installations are being made without the need for grant money. The main fuels are wood chip or wood pellets and these are readily available in most parts of New Zealand. There is the potential for specific energy crops to be planted to provide alternative biomass fuel. Wood energy case studiesA selection of wood energy projects supported by EECA are summarised below.Ernslaw Bioenergy - Mobile wood chipper Ernslaw Bio-Energy's new mobile wood chipper adds value to low-grade logs, producing about 13 tonnes of wood chips an hour. The chipper means Ernslaw Bio-Energy will be well-placed to take advantage of an expected increase in the use of wood-chip boilers. Pacific Wood Products - Smarter dust extraction New control systems on their extraction fans have cut Pacific Wood Products' energy costs and carbon emissions. The Ecogate system offers 42% energy savings, making the payback period just over four . Dongwha Patinna - energy audit unlocks $288,000 of savings A thermal energy audit of South Island MDF producer Dongwha Patinna identified seven energy management opportunities, and a buyer for excess fuel produced onsite - which together could be worth up to $288,000 a year. Cashmere High - Wood energy in schools Cashmere High School has future-proofed its energy supply by switching from coal to renewable wood energy to heat its classrooms. The new wood-fired boilers installed in May 2008 produce around five times less particulate emissions than a typical school coal boiler. Carbon emissions have reduced by 216 tonnes per year and the wood-fired system is 14% more efficient. Southern Pine - New wood fuel production Southern Pine Products is making the most of its waste products by turning MDF dust into combustible briquettes for boiler fuel. The saving in landfill costs is around $180,000 a year and the sale of briquettes provides a new revenue stream. Titoki Healing Centre - Wood energy in hospitality A wood pellet-fired boiler is proving considerably cheaper than electricity for heating the Bay of Plenty‘s Titoki Healing Centre. Fully automated and fed by a 3-tonne hopper topped up by the truckload, the 50kW system operates virtually hands-free and can also supplement the centre's solar-powered hot water system. |