Synergy has adopted the ISO9001 standard in order to demonstrate high levels of management quality. We believe that the future of the geothermal drilling indusry will belong to those companies that provide a consistent, high level of service to their clients
The following standards and guidelines represent major initiatives to drive up quality standards in the Ground Source Heating Industry.
Consumer confidence in our industry is essential to its long term growth and profitability.
Unfortunately, as with many emerging and "fashionable" technologies, the standard of implementation across the industry and country is, at best, variable with some companies cutting corners and botching installations, sometimes through simple ignorance or inexperience, sometimes simply to make a fast profit.
There are though, companies, like ours, who wish to achieve the best possible standards for the client. These are the companies that will strive to adopt the new standards.
Should you wish to obtain government funding contributions for your geothermal heat pump project, it is essential that you read carefully, and adhere to, the standards referred to below. Failure to do this will simply result in your application for government funding being refused.
Micro generation Installation Standard: MIS 3005
REQUIREMENTS FOR CONTRACTORS UNDERTAKING THE SUPPLY, DESIGN, INSTALLATION, SET TO WORK COMMISSIONING AND HANDOVER OF MICRO-GENERATION HEAT PUMP SYSTEMS
Synergy Boreholes and Systems Ltd. endeavors to adhere to the highest standards of operation when drilling, installing and commissioning geothermal borehole arrays.
We therefore welcome the introduction of new industry standards such as MIS 3005.
The majority of the provisions and requirements in this issue deal with the installation of the air/water/ground source heat pump unit, so do not apply directly to us as borehole array providers.
There are however, passages which detail the requirements that we should meet and the working values that we should use.
These are to be found primarily in sections 4.2.11 to 4.2.19 , 4.5.2 and 3 and Appendix C. as well as the supplementary ground loop look up tables.
We will strive to meet and comply with these standards in order to give our clients the assurance that the borehole systems that we install will perform satisfactorily for decades to come.
This new document will undoubtedly be refined over time. We will be compliant with the current requirements as soon as possible and in advance of many of our competitors.
The latest full version of these standards can be seen by clicking here
To see the supplementary ground loop look up table, click here
All of this may seem a little overcomplicated. In truth, it is not as simple as some heat pump salesmen, (or even some borehole drillers) may make it sound.
The most relevant passages of the MIS 3005 standards; Borehole array design parameters, materials, test procedures etc. are given here (Starts on page 19 of MIS 3005)
4.2.11 Designing ground heat exchangers is a complex engineering problem. If insufficient information is available to accurately design a ground heat exchanger, the installer shall adopt a conservative approach. For systems which require the heating capacity found in section 4.2.1 c) to be ≥30kW or incorporate ground loop replenishment through cooling or otherwise, the installer should undertake the design process making use of specialist recognised design tools and/or seek advice from an expert.
Synergy Note: Below 30 kW heat pump capacity, it is permitted to estimate borehole requirement using the tables provided in the MIS 3005. Above 30 kW you really need a professional design by a qualified and accredited designer, Synergy will be glad to help you with this.
4.2.12 Manufacturers‟ in-house software or other commercial software packages (such as EED, GLHEPRO, and GLD) may be used to design the ground heat exchanger provided that the software is validated for UK use and the following parameters are used for each installation:
- Site average ground temperatures (or annual average air temperatures). For horizontal ground loops, calculations shall incorporate the swing of ground temperatures through the year at the ground loop design depth.
- Site ground thermal conductivity values (in W/mK), including consideration of the depth of the water table; (this will normally require input from a geologist)
- An accurate assessment of heating energy consumption over a year (in kWh) for space heating and domestic hot water for the dwelling as built; (should be obtained from the architect, heat pump installation designer, or SAP report)
- An accurate assessment of the maximum power extracted from the ground (in kW) (i.e. the heat pump evaporator capacity); (Coefficient Of Performance, i.e. COP of heat pump to be used)
- An accurate assessment of the temperature of the thermal transfer fluid entering the heat pump. (see 4.2.13 below)
4.2.13 The temperature of the thermal transfer fluid entering the heat pump shall be designed to be >0oC at all times for 20 years.
Synergy Note: This is a new and most important design parameter requirement - must be adhered to!
4.2.14 Simplified design methods, including look-up tables and nomograms, should only be used where these have been designed and validated for UK ground conditions and installation practices and comply with clauses 4.2.12 and 4.2.13 in this standard. (look-up tables are provided in the MIS 3005 package)
4.2.15 If proprietary software is not being used, systems with a heating capacity ≤30kW that do not incorporate ground loop replenishment through cooling or otherwise shall use the following procedure for each installation for designing the ground heat exchanger (see note 1 below):
(a) The total heating energy consumption over a year (in kWh) for space heating and domestic hot water shall be estimated using a suitable method. The calculation shall include appropriate consideration of internal heat gains, heat gains from solar insolation, local external air temperature and the heating pattern used in the building (e.g. continuous, bi-modal, with an Economy 10 tariff or otherwise).
Note 1 This method has been designed to produce a conservative ground array design that should result in the temperature of the thermal transfer fluid entering the heat pump being >0oC at all times in the vast majority of circumstances. Use of improved design input parameters and more sophisticated design techniques may result in a superior outcome.
Notes on determining the total heating energy consumption
The Standard Assessment Procedure for dwellings is not designed to accurately determine the heating and domestic hot water energy requirements of real dwellings. It assumes a fixed dwelling location and estimates occupancy based on floor area. If the Standard Assessment Procedure is used to estimate the total heating energy consumption over a year for space heating and domestic hot water, it shall be adapted to account for changes in heating energy requirements resulting from the differences in external air temperature. Monthly average external air temperatures are given for various UK regions in appendix B.
EN ISO 13790: “Energy performance of buildings - Calculation of energy use for space heating and cooling” gives a method for the assessment of the annual energy use for spacing heating and cooling of a residential or non-residential building.
CIBSE Guide A contains comprehensive degree day information for different locations around the UK. Heating degree days can be used in conjunction with EN 12831 and an assessment of the appropriate base temperature to determine a building‟s heating energy requirement.
The International Ground-Source Heat Pump Association (IGSHPA) provide guidance on determining heating and domestic hot water energy production, electrical energy consumption and running hours using a temperature bin method.
b) The total heating energy consumption calculated in section 4.2.15 part a) shall be divided by the heat pump capacity selected in section 4.2.1 part c) to create a parameter called the “Full Load Equivalent Run Hours” (in hours).
c) The amount of power extracted from the ground is to be limited by the average ground temperature. If a full assessment of the average ground temperature is not being conducted, the annual mean air temperature for the appropriate UK region is provided in the tables and charts and shall be used as the estimate of average ground temperature. The data in the tables and charts is compiled by the MET Office; it is the annual average air temperature measured in a Stephenson Screen at 1.25m. The averaging period is nominally 1981 - 2010. See appendix B.
d) The local ground thermal conductivity (in W/mK) shall be estimated. The British Geological Survey keep logs from hundreds of thousands of boreholes from all forms of drilling and site investigation work; these can be used to estimate the depth and thermal conductivity of solid geology for closed-loop borehole systems. The British Geological Survey also compiles reports with information on the estimated thermal conductivity of superficial deposits for horizontal loop systems. Experienced geologists and hydro geologists will also be able to estimate the local ground thermal conductivity. For larger systems, it may be beneficial to conduct a thermal response test. The Ground-Source Heat Pump Association “Closed-loop vertical borehole design, installation and materials standard” contains guidance on thermal response testing. See appendix C for ranges of thermal conductivity for different rock types.
e) Using the information established in 2.4.15 parts b) - d), the look-up tables and charts provided for vertical and horizontal systems shall be used to establish the maximum power to be extracted per unit length of borehole, horizontal or slinky ground heat exchanger. Online versions of these tables are kept on the MCS website www.microgenerationcertification.org. Installers should check for the latest release of these design aids. The ground heat exchanger design shall be compatible with the notes accompanying the tables, for instance concerning the minimum horizontal ground loop or slinky spacing and minimum borehole spacing.
For horizontal ground loops, calculations performed to determine the maximum power extracted per unit length have incorporated the swing of ground temperatures through the year.
f) The seasonal performance factor, SPF, given in the heat emitter guide at the design emitter temperature should be used to determine the length of ground loop from the specific heat power extraction information found in the look-up tables and charts. The following formula shall be used to estimate the maximum power extracted from the ground (i.e. the heat pump evaporator capacity), G:
G = H ( 1- 1/HPF )
where H is the heat pump heating capacity determined in the section 4.2.1 c).
g) The length of the ground heat exchanger active elements, Lb (in m), is determined according to the formula:
Lb = G / g
where g is the specific heat power extraction from the ground (in W/m) found in the look- up tables. Lb is the length of the borehole heat exchanger; the length of pipe for the horizontal ground heat exchanger; and the length of trench required for the slinky ground heat exchanger.
h) For horizontal and slinky ground heat exchangers, the total ground heat exchanger area, A (in m2), is determined according the formula:
A = Lbd
where d is the minimum centre-to-centre spacing of the horizontal or slinky ground heat exchanger specified in the look-up tables and charts.
i) The minimum length of ground heat exchanger pipe in the active elements, Lp (in m), is determined according to the formula
where Rpt is a non-dimensional ratio. Rpt = 2 for boreholes; Rpt = 1 for horizontal ground heat exchangers; and Rpt is the minimum pipe length to trench length ratio specified in the look-up tables and charts for slinky ground heat exchangers.
j) The installer shall ensure that the flow of thermal transfer fluid is turbulent in the ground heat exchanger active elements. The viscosity of the thermal transfer fluid and therefore Reynolds number, which governs the development of turbulence, changes according to temperature. The Reynolds number of the thermal transfer fluid in the ground heat exchanger active elements should be ≥ 2500 at all times.
4.2.16 For all installations, should the geological situation on drilling or digging show substantial deviation from the conditions used in design or should drilling conditions become unstable or for some other reason
the target depth or area not be achieved, the design of the ground heat exchanger shall be recalculated and the installation revised or adjusted if necessary.
4.2.17 For all installations, the installer shall complete and provide the customer with Table 3, see below
4.2.18 For all installations, the hydraulic layout of the ground loop system shall be such that the overall system pumping power at the lowest operating temperature is less than 2.5% of the heat pump heating capacity.
The following table should be completed by the heat pump installer and borehole array designer / installer