NetGreen Heat

‘Netgreen Heat’ is a simple system of using any available solar thermal energy throughout the year for the use of heating of domestic hot water (DHW), Space heating of the house and during non Space Heating periods the Swimming Pool is heated.

An Auxiliary heating system will be also required to compensate for periods of the year when Solar Insolation is insufficient to support the total heating requirement plus during days when it is raining…

The Auxiliary system we promote is an Air Source Heat Pump, as the energy cost is the lowest possible when compared with other sources of instantaneous heating. If your house already uses low tariff electricity, we can significantly generate further reductions of energy costs.

Our Standard package, which our budget is based on, is the installation of:

  • A solar thermal collector system (limited by the collector area not being more than 40% of the area of your Swimming Pool)
  • 500L hot water cylinder for Space Heating thermal storage,
  • 300L hot water cylinder for Domestic Hot Water.
  • A 6kW Air Source Heat Pump with all related controls and pipework to integrate the system with your existing heating systems.
  • Three 2kW wall mounted Fan Convector Heaters (or ceiling mounted Fan Coil units), which can be placed any where inside your house
  • Heat Exchanger for the Swimming pool heating.
  • All Pump systems to circulate water through different systems.
  • Control System with related motorised valves and sensors.
  • All Pipework related to new and altered existing systems.

There are also variations available. Which options are available have been explained on the left side of this page – detailing the different Components that make up ‘NetGreen Heat’

The Standard Package is suitable to provide background space heating for most of the Space Heating period (October to April). The three 2kW Fan Convector heaters are usually positioned in the circulation areas nearest to the ground floor living areas (near lounge for example). The idea is to provide the core of the house a constant source of low cost heat to keep the heavy mass building fabric warm. The background warmth will permutate gradually throughout the house, assuming no areas of air infiltration or drafts are present in the house.

We have found from previous projects that additional heat is required only intermittently, during the few days when exterior temperatures fall to night time, minimum winter temperatures. Obviously this characteristic depends on the design and size of the house.

When the Standard Package of NetGreen Heat is installed and the house already has a Central Heating system, we usually advise that the Original Heating system should be left in place to provide this intermittent additional heat requirement. Though the Hot Water system (DHW) would be adapted to use Solar and Heat Pump energy rather than the Boiler.

We can provide larger systems, combining wall mounted Fan Convector Heaters (or ceiling mounted Fan Coil units) with Under floor radiant heating. Though it should be noted that Under floor radiant heating would require major civil building works, to enable installation.

Other additional options are available from providing a cooling system (Adsorption Chiller) that uses Solar thermal energy for its primary energy input, to a full Sustainable House makeover design assessment.

Solar Thermal Energy

The term solar thermal is used to describe a system where the energy from the sun is harvested specifically to be used for its heat. (The other main solar technology applied to buildings being solar PV that is used to generate electricity). Using solar energy to heat water has been commercially available in Europe for 40 years and is a proven technology. Portugal offers a good climate for solar thermal solutions benefiting from around 80% of the solar energy that is received at the equator.

The amount of solar radiation received (also known as 'solar insolation') is measured in kWh/m² (kilowatt hours per meter area) over a 24 hour period. For example during a July day in Cascais, on average, there would be over 6 kWh/m² of solar insolation. The main application for solar thermal in Portugal is for domestic hot water heating although there are 'combisystems' that use thermal stores that are directly linked in with low temperature space heating (such as Underfloor heating or Fan Coils). In extreme hot climates such as the Alentejo, Solar hot water can be used for generating Chilled water for cooling, using an Adsorption Chiller.

Combi Systems

A Solar Combisystem provides both solar space heating (and potentially cooling) as well as hot water from an array of solar thermal collectors, usually backed up an auxiliary non-solar heat source. The remaining heat requirement is supplied by one or more auxiliary sources in order to maintain the heat supply once the solar heated water is exhausted. For over a decade combi-systems have been installed in Gemany, Austria, Switzerland, Denmark, Sweden and Norway , even though these countries receive less solar energy than Portugal. From lessons learnt and the R&D undertaken different design criterias have been developed.

The size and complexity of combisystems, and the number of options available, mean that comparing design alternatives is not straightforward. We have selected a few of the options that are available.We have made our variation on a tried and tested design, which integrates a Swimming Pool to provide a heat dump during the Summer season.

Retrofitting existing heating systems

The cost of Energy is increasing every year, with the risks of Global Warming, so a replacement for the conventional Heating System with ‘NetGreen Heat’ is becoming a logical option to consider.

Just to heat the hot water for washing is becoming excessively expensive using the traditional systems, with estimated increase per year between 3 to 5% a year. The graph illustrates the costs using, Natural Gas, Bottled Propane Gas, Electricity and Heating Oil. A family of four will usually use approximately 200 litres of hot water a day.

The three Strategies below can assume that the Solar system will provide all the hot water capacity, throughout the year. Even if it is raining the Solar system should have sufficient solar radiation to generate hot water.

Three Replacement Strategies

Install our Standard Package:

Usually if a Central Heating system is already installed we make some pipe work alterations just to the Hot Water part of the system. The original hot water cylinder can usually be reused, with the option of using the original heating system as a last resort backup.

Our low temperature hot water circuit (circulating water at 40ºC) will not connected to the original heating system (usually circulating water at 80ºC), We would rather assume that the original heating system would be used when the exterior ambient temperatures were sufficiently low, for it to be turned on. Therefore the ‘NetGreen Heat’ Package system should be treated as a system to significantly reduce your energy costs, not provide all the required Space Heating for your house. See the ‘Costs and.Savings’ web page to get an idea of the estimated savings.

Replace the Radiators with Fan Convector Heaters:

On the assumption that the existing heating distribution pipe work can be reused and there is a plug point in the locality of each radiator position, the installation of the Fan Convector Heaters should be rapid work.

Each Fan Convector Heater can be controlled by a local thermostat and a programmable controller, with the additional option of further energy efficiency controls based on occupancy if required. The primarily method of responsive control shall be speed on the fan.

A larger Heat Pump unit will be required, to work in conjunction with Solar System, sized to the potential heat loss characteristics of the entire house. If advantageous the Boiler plant can be kept and integrated into the new system by providing a further option of Backup.

House Renovation or New Build:

We would suggest that our “Ideal System” be installed to give the comfortable and healthy environment, with the lowest running costs.

If the interior temperatures are important to keep cool during the Summer, the possibility of installing an Adsorption Chiller with some passive Architecture features should be strongly considered.