FAQ's
Q. What is Geothermal Heating?
A. Geothermal heating is a method of extracting latent low grade energy in the soil and utilising this energy to produce hot water for heating, or hot water for washing, baths and showers. The equipment used to do this is a called a Ground Source Heat Pump (GSHP) and Captors.
Q. What is a Ground Source Heat Pump?
A. A Ground Source Heat Pump is similar technology to an air source heat pump (normal Air-conditioning unit). However as the winter air temperature can vary depending where you live, from +15 °C to -15°C, the ground temperature remains relatively stable allowing high efficiencies and consistent performance.
Q. What is a Captor?
A. The Captor is the means by which heat is collected from the ground. This consists of buried pipe(s) used to transfer the energy from the ground to the Geothermal Generator unit. These pipes can be made from either copper or high density polyethylene (HDPE) and use either refrigerant (copper) or a water/glycol mixture (HDPE) to collect and transfer the heat. Captors can be laid horizontally or vertically.
Q. Are a lot of earthworks required?
A. Not necessarily, compared to other systems that can have pipes buried at depths of up to 2m. Next Energy utilise systems designed to have horizontal captors buried at only 50-60cm deep. This allows for minimal earthworks, saves on installation costs and suits the New Zealand climate well, as we don’t have the harsh winter temperatures of Northern Europe / North America.
Q. Can you bury the Captor as deep as you want?
A. No, Next Energy install systems that have been developed over many years to give optimum all year performance at a depth of 50cm-60cm. This method best utilises solar gain and rain fall to replenish the grounds energy.
Q. Surely burying the captor at 2m would give the best efficiencies in winter?
A. There may be some small gain in the coldest parts of the country at initial start up. However as stated above, having the captor closer to the surface will allow quicker recovery of the energy in the captor field
as it is used. A consideration of installing too deep is that a larger area will be required for the captor, to prevent performance declines during the heating season. Too small an area and the ground can freeze around the captor and not thaw making the system less efficient.
Q. Will the ground freeze and damage my plants?
A. As part of the normal operation of a Ground Source Heat pump, the soil immediately around the Captor pipes does freeze, however as the system completes its cycle the soil draws heat from the surrounding area and the soil thaws naturally. At a depth of 50-60cm the pipes are well away from any plant or grass roots. There are however restrictions on the distance the captor field has to be from trees, water/ sewer pipes and foundations.
Q. Can energy be taken from the ground when there is frost and snow in winter?
A. Absolutely, unlike Solar, Next Energy Ground Source Heat Pump systems do not require the use of boost elements under normal running. The systems are designed so there is always sufficient energy stored in the ground to be recovered.
Q. We have a driveway to be covered by concrete, can we bury the captor under here?
A. No, captors need to be buried under permeable ground as it is largely the rain which transfers heat back into the ground. It is also the moisture in the soil which helps transfer heat into the captors, under drive ways this moisture can be lost. If your driveway is to be chips or stone or another permeable material that allows rain to filter through, then this could be an option.
Q. Can I have one unit for hot water for a baths and showers etc. and In-floor Heating?
A. In order to maximise efficiencies Avenir Energie have developed separate units for both of these applications. There is a dedicated hot water unit for baths and showers etc. They also have a large range of units for In-floor heating and Radiators including High Temperature units. In some circumstances it may be practical to use just one unit (High Temperature), but in most circumstances it is better and often cheaper to have the separate units.
Q. Will I need to boost the hot water with electric elements as with Solar?
A. No, the DHW60 unit is capable of supplying 60°C hot water for a 300L mains pressure cylinder, suitable for a family of 4-6, without the need for boost elements, day or night, summer or winter irrespective of the weather conditions. The cylinder does however include heating elements that are wired up as normal during installation. These are left turned off as a redundancy and can be switched on should for any reason the geothermal system be out of service or for maintenance.
Q. Can I use my standard cylinder?
A. In some circumstances yes, usually if it is a reasonably new well insulated cylinder. The Next Energy DHW60 is however usually supplied with a purpose designed stainless steel mains pressure cylinder to best optimise the efficiencies to be had. We are happy to advise on your present cylinder.
Q. How big an area do I need for a hot water system?
A. For a domestic hot water unit (DHW60), the area required is approximately 35m², however this could be a trench approximately 43m long by 45cm wide.
Q. How big an area do I need for the heating system?
A. As rule of thumb, you will require approx 20m² per kW of heating load. The heat loss form a reasonably well insulated new house is approximately 80Watts /m² of heated area, therefore a heated floor area of
200m² would require a captor area of approximately 320m². Good insulation levels can significantly reduce heat loss therefore reducing the size of the GSHP and the captor area required.
Q. If this is new technology, will it work here in New Zealand?
A. The technology has been available in Europe and North America for over 20 years and has proven itself in the harsher climatic conditions of Scandinavia and Europe. Next Energy GSHP’s are made by Avenir Energie a French company with many systems installed in Switzerland and Germany amongst other countries. By comparison, New Zealand has a much warmer winter climate and ground source heat pumps therefore, are very effective here.
Q. If I have an existing in-floor or radiator heating system run from gas or diesel boilers, can I convert to a geothermal system?
A. Yes subject to you having a big enough captor area, we will also require some information on your current system to assess the size of unit required and the temperature it needs to run at. We would be happy to advise.
Q. How does a Next Energy Geothermal system compare with Gas or Diesel boilers on capital and running costs?
A. Depending on the size of unit required and the complexity of the system, the Geothermal system is likely to be more expensive to purchase. However as we have seen recently Gas and Diesel energy is becoming ever more expensive to purchase, without a surety of supply into the future. Once installed a Next Energy Geothermal system will utilise the free energy stored in the ground and only requires a small amount of electricity to run the system. As owner of your land, you are also the owner of your own heat source. Also given New Zealand’s largely renewable electricity supply, the units are very environmentally friendly.
Q. How do I go about obtaining more information and receiving a quote?
A. Next Energy will, upon receipt of your building plans, perform a heat loss calculation and heating system design. From this we will provide an obligation free quote or estimate. This can then be discussed with you and your Architect to tailor the system to suit your needs and to maximise the benefits of this Next Energy heating system. We are able to provide a full in house design, supply and install service giving you the peace of mind of dealing with an established group of companies. To complement the geothermal units we have a full range of in-floor heating pipes, aluminium low temperature radiators, energy efficient manifolds and the latest technology energy efficient pumps.
Q. What Am I waiting for?
A. Sorry, we have most of the answers! This one is down to you.
