Solar Photovoltaic Electricity Generation for Dairy Farms

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1 Improving the Welsh Dairy Supply Chain Solar Photovoltaic Electricity Generation for Dairy Farms

2 Dairy Development Centre Gelli Aur Carmarthen Carmarthenshire SA32 8NJ Telephone: July 2012 The Dairy Development Centre (DDC) acknowledges the contribution made by Farm Energy to the technical content of this booklet. This project has received funding through the Rural Development Plan for Wales which is funded by the Welsh Government and the European Agricultural Fund for Rural Development. No part of this publication may be reproduced or transmitted in any form by any means without the prior written consent of the Dairy Development Centre. Whilst all reasonable care has been taken in its preparation, no warranty is given as to its accuracy, no liability accepted for any loss or damage caused by reliance upon any statement in or omission from this publication.

3 Contents What is the Feed-in Tariff scheme? 4 Panel positioning 5 Electrical installation issues 6 Energy generation 6 Other costs 7 Financial considerations 7 Application to dairy farming 8 Solar PV electricity generation for dairy farms 3

4 Generation of electricity from renewable sources has become more financially attractive since the introduction of generation subsidies called Feed-in-tariffs (FiTs). Photovoltaic (PV) panels are an attractive technology for farmers with buildings or areas of land suited to the installation of arrays. Installation is straightforward and they are, for the most part, a fit and forget solution to renewable energy generation. What is the Feed-in Tariff Scheme? A FiT is paid for each kilowatt-hour (kwh) of renewable electricity generated from an eligible renewable scheme. Rates are technology and size specific. Since the scheme started in 2011 the rates have been reviewed several times and further changes are expected in the future. The FiT rate is fixed at the time of project registration, index linked and are currently paid over a 25 year term, although this is likely to be reduced to 20 years in August 2012 to bring it in line with other renewable technologies. 4 Solar PV electricity generation for dairy farms

5 Panel positioning PV panels can be installed on a building roof - ideally south east to south west facing, with a 20 to 50 degree tilt. Ground-mounted systems are also available, which can be ideally placed and orientated. An area of approximately 8 m 2 per kw of peak capacity is required. So for example a 50 kw system would require 400 m 2 to accommodate between 180 and 250 PV panels on a roof. Panel weight is approximately 15 kg/m 2. Any building older than 10 years may be rejected by an installer as not being robust enough to bear this load. The map represents the yearly sum of irradiation on horizontal and optimally angled panels, over a 10 year average [kwh/m 2 ]. The same colour legend also represents potential solar electricity [kwh/kwp] generated by a 1kWp system per year with photovoltaic panels mounted at an optimum angle and assuming system performance of 75%. For a system to be successful there must be no overshadowing, for example from trees or other buildings. PVGIS European Communities, Solar PV electricity generation for dairy farms 5

6 Electrical installation issues PV panels produce direct current (DC) so they use inverters to convert the output to mains voltage - alternating current (AC). The inverter is connected in parallel with the mains supply and energy generated either displaces that which would normally be CASE STUDY purchased, or is exported when on-site generation is greater than site demand. A protection system is required to prevent the system back-feeding into the grid should the grid fail. The electricity supply should be at least 1.5 times larger than the maximum PV array output i.e. 15 kilovolt-ampere (kva) for a 10 kilowattpeak (kwp) system. For systems over 15kWp the electricity supply will probably need to be three-phase. If you have to upgrade the supply, the distribution network operator will charge you for the upgrade and this can be expensive. Energy generation PV cannot be regarded as a means to energy self-sufficiency as it only operates during daylight hours and its output is dependent on the elevation of the sun and cloud cover. Roughly speaking a typical photovoltaic system will produce an average of about 9% of its theoretical maximum output in the UK. There is a published Standard Assessment Procedure (SAP) which will estimate the likely output of a system depending on its rating, latitude and Mr and Mrs Price from Brecon installed a solar PV system on the roof of one of their farm buildings in March Mr Price said: We knew that we wanted to install some form of renewable technology and solar PV fitted our needs. A local company did the installation and they were very professional. To date we have generated almost 1,700kWh of electricity which has reduced our electricity bill by around 105. We are very pleased with the system and are happy with the investment that we have made. Income plus savings for the period March July 2012 generated through FITs: Generation tariff = 736 Export tariff = 26 Electricity bill savings = 105 Total income & savings to date = 867 orientation. Please visit the following webpage address for further information: Output from panels will fall over time, at a rate of approximately 0.8% a year or 20% over their 25 year lifespan. 6 Solar PV electricity generation for dairy farms

7 Other costs Operation and maintenance costs are usually estimated at between 1% and 2% of the total installation cost per year. Although PV panels can last 25 years, the lifetime of the inverters (converts Direct Current to Alternating Current and are vital components of any PV system) will be shorter, possibly only 10 years. Financial considerations You should consider the energy related income that comes from the generation tariff (FiT); the excess energy that is exported to the national grid (export tariff) and the energy savings from not having to purchase as much energy from your dedicated energy supplier. The basic economics of a 49kW system installed in April 2012 are as follows: Installation costs 73,500 Likely costs (2012) are 1,500 per kw installed Average energy generated per year 38,631kWh 9% of theoretical maximum generation (average for the UK) Average annual income from FiT 8,460 Generated kwh at 21.9p/kWh Average annual income from power sold 898 Assumed 75% export at 3.1p/kWh Offset electricity value 1,060 Average maintenance cost 1,600 Annual value to the farm 8,818 Assumed 25% own use at 11p/kWh Cleaning, repair and system checks (FIT income) + (export) + (offset) - (maintenance) Payback 8.3 years (Install cost)/(annual value) Solar PV electricity generation for dairy farms 7

8 Application to dairy farming Even at peak annual generation times, normal dairy farm energy use doesn t suit solar energy production. On a typical dairy farm energy demand will be at its peak during morning and evening milking, where as solar energy production is at its peak around the middle of the day. Nevertheless, returns on investment can still be acceptable. It is possible to alter the operation of equipment such as water heaters and ice builders to make the best use of the PV generated electricity. By doing this the return on investment will be quicker as electricity used on farm from the PV is worth more than selling any unused energy back to the electricity supplier. Application of solar PV on dairy farms - normal energy use Electrical energy (KWh) 00:00 01:00 02:00 1st milking Milk collection 2nd milking 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 Un-used solar energy 13:00 14:00 15:00 12:00 Time 16:00 17:00 18:00 19:00 20:00 21:00 normal energy use solar PV generation 22:00 23:00 20:00 Application of solar PV on dairy farms - revised energy use utilising solar PV Electrical energy (KWh) 00:00 01:00 02:00 1st milking Un-used solar energy Milk collection 2nd milking 03:00 04:00 05:00 06:00 07:00 08:00 09:00 10:00 11:00 In order to maintain the best performance from the PV array, it is likely to need cleaning on a regular basis especially in the summer when dust can be an issue. Reference Šúri M., Huld T.A., Dunlop E.D. Ossenbrink H.A., Potential of solar electricity generation in the European Union member states and candidate countries. Solar Energy, 81, , 8 Solar PV electricity generation for dairy farms 13:00 14:00 15:00 12:00 Time 16:00 17:00 18:00 19:00 20:00 21:00 normal energy use solar PV generation 22:00 23:00 20:00 Graphs for illustration purposes only.