With the world at six billion and growing, not only do we need to secure a continuous electricity supply, we also need to ensure our energy sources are ‘eco-efficient’.
This means adopting alternative sustainable power sources, an area where small farm holders can have more opportunity than city dwellers.
In NZ where electricity demand is projected to increase by 45% to 50% by 2025, currently nearly two thirds is produced by renewable sources, mostly by hydro systems (well ahead of the rest of the world), with the balance from burning gas, coal or oil at power stations, wind power contributing about 3%, along with a small amount generated by geothermal sources and biomass.
To prepare for the future, the Government has allocated $6.7million a year towards the development of sustainable options like liquid biofuels, solar, hydrogen, windpower and low carbon fossil fuels.
At the same time, the NZ Energy Efficiency and Conservation Strategy (EECA)
is encouraging wind, micro-hydro, solar power, and potentially bioenergy, as localised renewable energy supply options for individual remote dwellings or communities.
Certainly, wind power is one of the best renewable forms, because it will never run out and does not emit anything into the atmosphere or waterways. And the fact that NZ lies across prevailing westerly winds, means we have one of the best wind resources in the world.
New Zealand Wind Energy Association (NZWEA) explains that the average grid connected household uses about 20 kilowatt hours (kWh) of electricity a day, which a 5 kilowatt (kW) wind turbine is often able to supply.
Wind turbine designs suitable for farms, come rooftop mountable and free-standing.
Lines company Vector, has launched a year’s trial of ‘Swift’, suitable for individual property owners, this is one of the first silent small rooftop wind turbines. www.vector.co.nz
Vector’s Joanna Anderson, says the key is finding a site with a good wind resource and a suitable mounting point. As with large hilltop wind farms, positioning of micro wind turbines is critical. The less sheltered the site with unobstructed air from the direction of the prevailing winds the better, which means being clear of buildings, trees and embankments.
Mounting directly on to a building lowers installation costs and allows for direct use within the building of the electricity generated. Where the building is grid connected, the Swift connects to the building’s electrical wiring through an inverter and operates automatically parallel to the grid supply, displacing electricity that would otherwise be sourced from the grid.
“If more electricity than the building is using at any time is generated, the excess electricity simply flows back in to the grid. Users can be credited for the value of the excess electricity, which is effectively "sold back" to their retailer, by having an agreement with their retailer and electricity meters in place to measure power flow separately in each direction. Where it isn’t possible or it’s too expensive to provide a grid power supply, this can also work as part of an off-grid system”.
A free-standing wind turbine designed specifically for farmers and people in remote locations has been introduced by Energy Recovery Engineering and Construction Limited (EREC). The twelve metre high turbine can be erected without a crane and easily maintained by its owner. The mast pivots in the middle to enable raising and lowering of the unit for installation and maintenance. The turbine can generate enough electricity to power three houses and any excess power may be sold back to the national grid.
The EECA has produced a ‘Remote Area Power Systems’ and a ‘Stand Alone Power Systems” fact sheet, including information for people interested in installing small-scale wind turbine power systems. www.eeca.govt.nz
As the most abundant energy source on the planet, solar energy is another excellent renewable power source option.
Solar water systems are improving all the time. Not only are new designs better priced, but they are frost protected, constructed mainly of recyclable materials and have evacuated tubes, which don’t have water running through them, so are lighter on your roof.
The Consumer Institute say even in less sunny areas, a solar water system can provide between 50% to 75% of individual yearly hot water needs, cutting about 2200kWh from annual electricity use
Solar energy, where sunlight is converted directly into electricity, is collected in Photovoltaic (PV) cells, usually bolt-on panels placed on the roof or somewhere nearby where there is best access to the sun.
If you have a flowing stream on your property, a micro-hydro scheme could be the answer, generating up to 10 kW of electricity, providing sufficient energy to meet your needs, depending on individual usage. The system involves water flowing downhill through pipes into a small turbine, which drives an electricity generator and will require a resource consent. www.smarterhomes.org.nz
Power generated by wind turbines, solar energy and micro-hydro systems, is not generated continuously and the direct current (DC) output needs to be stored in a bank of batteries. If conventional appliances using alternating current (AC) are used, an inverter is needed to convert from DC to AC.
Properties on Great Barrier Island rely on stand-alone power systems, combining renewable energy forms and energy efficient technologies, usually backed up by a diesel or petrol-driven generator.
The other EECA recommendation, bioenergy or biofuel, produces mainly ethanol from specially grown crops like corn and cereals, or from farming residues like straw, livestock slurry and chicken litter or from wood waste or whey from the dairy industry. http://www.bioenergy.org.nz/
What do the experts have to say? Stephen Hallett of Alternative Power Solutions Ltd, sums it up perfectly. www.alternativepowersolutions.co.nz
“Being rural, a hybrid system using a combination of renewable energy sources is likely to be a more viable option as there are usually alternative locations for generation equipment, for example wind generators, which would not be practical in an urban environment. Plus, there may be access to a stream for hydro generation and a combination of energy sources gives greater power supply reliability than a single source”.
Mr. Hallett suggests, a stand alone system is most likely the best option for rural installations, although if a mains electricity supply is available and there is a good source of generation, a grid interactive system could work well.
“In either case the system still needs to designed correctly for the application so it will meet the expectations of the end user. The inverter, be it stand alone or grid interactive, needs to be sized to meet the continuous demand. Also the short term surge demand placed on it and batteries, especially in a stand alone application, needs to be sized correctly for the potential generation, the expected daily load and the length of time you can expect to have no generation from any of your energy sources, for example, overcast windless days. It is important to get the battery bank correct as you can not add batteries to the existing setup later on”. New batteries placed with a string of older batteries will drop to the performance level of the old ones.
Generally, many environmentally sensitive energy efficient ideas can be incorporated into new and existing homesteads, starting with water heating accounting for around 40% of our power bill. Using a continuous flow system, either LPG or Natural Gas, where the water flows over a heating element and is heated as you need it, is estimated to save about half the cost of a traditional storage cylinder system.
We can opt for natural cost effective heating like heat recovery ventilation (HRV) by using the free heat generated in the roof space by the sun.
Solar heating catches heat from the prevailing sun on a large area like the roof and passive solar heating makes the most of the sun’s heat in our living space.
Adding insulation and using energy efficient lighting are helpful for an existing homestead. Building new to face north to make use of passive solar energy and using double glazing including windows with a metal film to reflect heat back into the rooms and more durable aerated concrete block instead of timber, offer long term benefits.
Heat pumps, solid fuel appliances like wood pellet burners and low emission wood burners, and flued gas are further cost effective environmentally friendly ways of general heating.
The right appliances can also contribute to energy conservation. Today, washing machine and dishwasher appliances are designed to save energy and water.
There’s also nuclear power, described as the most environmentally benign way of producing electricity on a large scale, but involving waste products and the danger of releasing radiation into the environment.
Surprisingly it is possible to purchase a small unit for individual properties, however, as you would imagine, it is not possible to lay your hands on the uranium to power it.
©2008 Linda Donald
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Appeared in New Zealand Lifestyle Farmer
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