WHAT IS GROUND SOURCE HEAT?
Heat pumps in general and ground source heat pumps (GSHP) are effectively reverse air conditioning systems. They use low temperature heat and convert it into a much higher and hence more useful temperature that can be used for water heating and general domestic heating.
Using initial energy from the lake, together with the high efficiency of the heat pumps saves a large amount of carbon dioxide emissions that would otherwise be expelled into the atmosphere under traditional heating systems. The high efficiency of the ground source heat pumps minimises the electricity demand, and the respective CO2 emissions that goes with it.
Ground source heat pumps yield emissions of 0.12Kg of CO2 for every kwH of useful heat delivered, whereas high efficiency condensing boilers yield 0.23Kg of CO2 for every kwH. This shows that the CO2 emissions from high efficiency boilers are almost double that of ground source heat pumps for the same unit of heat delivered.
GROUND SOURCE HEAT PUMPS HAVE OTHER ADVANTAGES:
High level of reliability - due to few moving parts and no exposure to weather
High level of security - there are no visible external parts that can be damaged or vandalised
Long life expectancy - normal life span of 20-25 years; the loops in the water have a life span of up to 50 years
Low noise levels
Low maintenance costs - no requirement for regular service
No need for boiler or fuel tank
No combustion or explosive gases within the building
No flue or ventilation requirements
No local pollution
WHY CHANGE, AND WHY GROUND SOURCE HEAT?
A change of heating system at Castle Howard from oil fired to another system was required to help reduce overall expenditure. The project also aimed for an improved carbon footprint as well as affording an opportunity for educational purposes.
A feasibility study of all the alternativesto oil produced a recommendation for a wood burning system. However the high expenditure required for a refurbished and enlarged boiler house, as well as some concerns over the running costs of the system resulted in the project being abandoned.
Ground source heat systems run at between 50 degrees and 65 degrees. The existing oil-fired system was running at 75-85 degrees and on time clocks. The whole system was also governed by thermostatic controls throughout the house. To prove whether or not a ground source heating system would work in Castle Howard, the boiler temperatures were reduced to 55 degrees and all the time clocks removed so that the system would run 24/7.
The results were as follows;
• the fuel consumption reduced from 85,000 to 55,000 litres per annum in 2006. In 2007 and 2008 it was around the 65,000 mark both years as the winters were colder.
• the temperature in the house was comfortable, even during the colder periods.
• the humidity and temperature recordings both showed a more stable environment, resulting in better conditions for the works of art.
• the boilers worked more efficiently, resulting in fewer problems and therefore less maintenance.
The conclusion reached was that if a ground source heating system was to be introduced, then it would work, and at the same time drastically reduce the estate’s overall consumption in oil with all the resulting benefits that would entail.
RESULTS
Oil costs versus Ground Source Heat electricity costs.
• Kw usage reduced by c.50%
• Carbon output reduced by c.60%
• Expected payback on project c.5 years
HOW AND WHERE?
The project required 3 phase electricity and running water. The former was already supplied, and the latter was available in the form of the pond 250m immediately to the North of Castle Howard. The pond had to be drained and dredged prior to the installation of coils through which glycol would be pumped to extract the energy from the water.
From the pond the pipes were run to a manifold chamber, and then from there to the house at 1m depth. (As a Grade 1 Park and Garden, planning consent was required to dig the trench and this was granted subject to an Archaeological Watching Brief) The Castle Howard Building Services and Gardens teams undertook the digging and relaying of the trench for the pipes.
From the trench the pipes were fed in to the basement of the house where they were connected to two heat pumps, which were then coupled to the existing heating system.
A local contractor carried out the electrical work for the installation of the heat exchangers in conjunction with Ecovision’s engineers. A local self-employed plumber was responsible for the installation of the pipe work under the supervision of Ecovision’s engineers.
2009 TIMINGS AND COSTS
FEBRUARY
• Discussions with Ecovision Ltd commenced. Potential grants, loans and other funding identified. Feasibility study with payback
model produced.
MARCH
• Initial quotation of £135,000 received. Castle Howard extra costs identified to be c.£50,000.
MAY
• CERT grant of £50,000 confirmed by Scottish Electric accelerating project timing.
• Application to Carbon Trust for interest free loan of £100,000.
• Application to North York Moors National Park Authority Sustainable Development Fund (NYMNPA SDF) for £10,000 grant.
• Ecovision Ltd quote acceptance.
• Removal of old boilers and pipe work.
• Application to Ryedale District Council for planning permission to dig trench.
• Lake drained. Completed 5th June.
• Pipe work, heat pumps, and buffer tanks installed. Completed 19th June.
• Lake dredged. Completed 26th June.
JUNE
• NYMNPA SDF grant approved.
• Carbon Trust loan of £59,259, interest free and repayable over 3 years, offered and accepted.
• North Yorkshire County Council require an Archaeological Watching Brief as a condition for planning permission.
• Archaeological Watching Brief tender document received and Written Scheme of Investigation submitted to planners.
• Placement of first coils in the lake.
JULY
• Planning permission granted.
• Archaeologist on site until 10th July
• Started digging trench and pit for manifold chamber. Completed 15th July.
• Pipes connected and laid.
• Trench backfilled and turf restored. Completed 3rd August.
• Pipes in lake and pipes to house connected in manifold chamber.
AUGUST
• Pipes filled with Glycol.
• System switched on.
• System commissioned.
• Archaeological Watching brief delivered to Castle Howard Estate Ltd, Ryedale District Council, and North Yorkshire County Council.
SEPTEMBER
• 9th September - Hot water switched from oil boiler to Ground Source Heat(GSH) system.
OCTOBER
• 1st October - Heating switched on through GSH system.