RENEWABLE ENERGY SYSTEMS
Early
on in the development of Castlehill Heritage Centre it was decided that
every effort should be made to adopt a sustainable approach to the construction
and operation of the facility. Consistent with this the Society have a
vision of ultimately meeting the majority of energy needs of the Centre
through the utilisation of renewable energy sources for space heating,
domestic hot water and lighting.
The renewable energy systems will be developed and installed in stages, the initial stage being the installation in 2008 of a biomass central heating boiler to provide building heating.
In December 2011 we took full advantage of the renewable energy incentive schemes on offer at the time by installing 18 photovoltaic panels on the south facing roof above the main exhibition hall. The installed capacity is 4kw.
Subject to capital funding being available, installation of further renewable technologies such as solar water heating, a mirco wind turbine, and potentially a ground source heat pump system, will be considered in the future. Such systems would further reduce reliance on finite fossil fuel energy sources thereby minimising the impact of the Castlehill Heritage Centre on our environment.
Additionally, Castletown Heritage intends to configure the renewable energy systems as an educational resource, and to this end propose to incorporate an interactive computer based monitoring and display system. This will enable the Castlehill Heritage Centre renewable energy systems to form the basis of studies into the practical aspects, efficiency and utilisation factors of the various forms of energy source in our local environment.
After researching possible heat sources such as wood chip, wood pellet and ground source heat pumps the Society engaged a professional, registered, renewables installer/consultant Peter de la Haye Engineering to design and supply a biomass log boiler system to provide building heating and hot water. The choice of a biomass log boiler and associated hot water accumulator was based both on a well proven concept and the opportunity to maximise local community engagement and support through the sourcing of log fuel from the nearby Dunnet Forestry Trust.
The project was developed with the support of and to meet the requirements of the Scottish Community and Householders Renewables Initiative (SCHRI), which is managed locally by HI-Community Energy Company - North Highlands and who awarded grant funding for the project. Match funding was awarded by the Highland Council through the Landward Caithness Ward 4 Discretionary Budget.
To
minimise expenditure, the system was installed over a period of five weeks
by skilled Society members working in their spare time. On completion
the installation was inspected, commissioned and certified by Peter
de la Haye, thereby ensuring the appropriate technical, installation
and system performance standards were met. This approach was agreed with
HI-CEC.
The photo shows Peter (left) handing over the completion certificate to Neil Buchan, CHS Technical Projects Manager. CLICK HERE for photos of the installation works and completed system.
System Concept
The system design is based on the installation of a 50kW Baxi Solo Innova 50 log boiler coupled to a hot water accumulator, which has been sized at 3,000 litre such that the boiler only requires to be fired once per day in the depth of winter. This approach will significantly reduce the operational burden on the volunteer staff manning the centre. Hot water for the underfloor heating system is drawn directly from the accumulator through a temperature balancing system. The domestic hot water is heated indirectly via a heat exchange coil within the accumulator. These are standard arrangements.
Operation of the system has proven to be simple and reliable. One firing of the boiler per day during the winter months reduces to once every four days during the summer. The system always provides sufficient heat to maintain a very comfortable 20 deg Centigrade within the Centre 24/7 and plenty of hot water. Combustion of the logs (which are partly gassified) is total, with only trace ash powder and no smoke generated once the boiler is up to temperature.
We have had quite a number of visitors who were considering the installation of a log burner, to the see our system in action. So far everyone has been impressed!!
As discussed above, the system has also been designed to accommodate future addition of other renewable energy sources, which will be developed as funds become available. Such potential sources may include solar water heating, a ground source heat pump and ultimately, a micro wind turbine.
In preparation for, and to complement and maximise utilisation of the renewable energy sources, the space heating design for the Castlehill Heritage Centre is based on the use of warm water (~50 deg C) underfloor heating, coupled with a high standard of installed thermal insulation. The underfloor heating system operates by circulating warm water through pipes buried in a sand screed underneath the floor surface. Heat transfer to the room occurs principally by radiation over the whole floor surface (as compared to a conventional radiator system which transfers heat mainly by convection from a very small hot surface). Air temperature at working level is therefore very even throughout the room.
Not only is underfloor heating very efficient, using typically 10-15% less energy to achieve the same comfort conditions as compared to radiators, but the relatively large thermal mass of the floor structure operates as a secondary heat store. This assists the creation of a stable ambient environment within the building, essential to the preservation of the artefacts to be displayed and archived within the Castlehill Heritage Centre. The underfloor heating system also brings the added benefit of maximising the useable floor and wall space within the building, as there are no protruding radiators or pipe work.
The
underfloor heating system for the Heritage Centre was designed and supplied
by Ullapool-based Invisible
Heating Systems who provided full technical support and advice
during the process.
IHS specialise in the design of a range of fully integrated micro-renewable heating and cooling systems including underfloor heating, ground source heat pumps, solar panels and domestic water system. The company also delivers advice and consultancy services on a wide range of energy efficiency matters and is widely regarded as an industry expert in heating and cooling efficiency methods.
Because of its low
energy consumption, underfloor heating is probably the closest you'll
get to an ideal heating system. With underfloor heating, the room thermostat
can actually be set 2-3ºC lower than a radiator system. With modern building
methods and improved levels of insulation, it's extremely compatible with
other energy efficient heat sources such as heat pumps, solar panels and
condensing boilers. 
In Castletown Heritage Centre, the underfloor heating pipework was attached to a layer of insulation and embedded in sand. The sand is used as both a heat store and emitter. This method works extremely well with the selected floor covering - flagstone. Using sand is more environmentally friendly than using a cement screed (due to the latter's production process).
In addition, the system consists of a self-regulating 8-group manifold with simple "plug and play" roomstats and control clock. Even when the system is timed to be off, it maintains an ambient temperature of 4ºC below its normal operating temperature thus maintaining a constant level of heat in the building. This reduces the length of time required to heat up the system when required, thus reducing fuel usage.
For further information about Invisible Heating Systems and the system design and services they offer, see www.invisibleheating.co.uk
Our
latest renewable project was the installation of 18 photovoltaic panels
with a maximum generation capacity of 4kW on the south facing roof above
the main exhibition area. The output from the panels is converted from
a DC voltage to standard mains 230V AC using an inverter, the output of
which is connected in parallel with the incoming mains electricity supply.
The
amount of energy generated is recorded on a Watt-Hour meter, and under
the current HM Government scheme we get paid a feed-in tariff for each
unit generated. The normal incoming S&SE meter records the amount
of energy that has been imported from the mains supply - i.e. the
arithmetic sum of the energy being demanded by the Heritage Centre, less
the amount of energy being generated by the PV panels, at any point in
time.
So our electricity bill only reflects the units we actually import, and we get a cheque every three months for the units we generate - it's a win-win! Unfortunately the S&SE meter doesn't run backwards on bright sunny days....
