Farming for a Sustainable Future

by the CADDET UK National Team

Introduction

West Beacon Farm is the family home of Tony and Angela Marmont but it is a home with a difference; they have converted their house and land into a prime example of renewable energy utilisation combined with other energy efficient practices. The working farmstead has an area of 20 hectares set in an area of natural countryside. The Marmont's aim is to enhance the natural ecology and achieve a sustainable lifestyle.

Natural Resources

There are eight hectares of permanent natural pasture and 20,000 recently-planted broadleaf and evergreen trees for natural ecology, carbon dioxide uptake, bird life and small mammals. Dead and waste wood from the trees can be used for firewood as a biomass resource. The lake has been formed from a natural spring. It provides a habitat for aquatic life, including trout for food, and is the source of energy for the heat pump which contributes to household heating.
 The original farmhouse has been extended. At the west end, a very large conservatory has been built above the engineering plant room and garage below. The conservatory traps solar heat even on a cloudy day. This heat is controlled by automatic fans and shutters and the heated air can be passed into the main house for winter heating.
 The water supply to the house is pumped from a natural well 50 m deep to a reverse-osmosis membrane water purifier. Only pure water passes through the membrane, leaving contaminants and dissolved chemicals to be discharged as waste.

Renewables Technology

An evacuated-tube solar collector is mounted on the roof of the plant room. This supplements the domestic hot water circuit which is supplied principally by a heat pump which removes heat from the lake and transfers it to the house for hot water and heating. Typically 3-4 units of useful heat are produced for each unit of electricity consumed in a heat pump.
 A combined heat and power (CHP) unit generates 15 kW of electricity and provides 38 kW of heat to the household heating system and to the plant room. There is the possibility of using gas from a biomass gasifier or hydrogen from an electrical electrolyser to fuel the CHP unit. Next to the CHP unit is a battery charger which can recharge the battery from the CHP unit, the wind turbines or the grid.
 Two wind turbines, each capable of generating up to 30 kW of electricity, export about 80% of their output to the local electricity grid under the terms of the UK's Non-Fossil Fuel Obligation (NFFO). the remainder is used on the farm. Under the NFFO scheme, regional electricity companies are obliged to accept electricity generated from renewable sources by private generators. The wind turbines were manufactured by Carter Wind Turbines Inc (now Carter Technology).
 An array of photovoltaic cells converts sunlight directly into electrical power. The 120 V dc electricity produced passes to the plant room to charge a large battery of lead acid cells if required. Otherwise, the electrical power passes to two inverters to produce 240 V ac (single-phase) for domestic use and 415 V ac (three-phase) for farm use.
 In the plant room, automatic control and monitoring equipment has been installed by Loughborough University; this monitors the whole system. By first analysing all the technical processes, an economic optimisation can be made for integrating the whole system, including electricity sold to the grid.

Energy production

289,010 kWh
 (263,848 kWh wind; 25,162 kWh solar)

Exported to the grid

198,588 kWh

Estimated Coal saved

60-80 tonnes

Estimated CO2 saved

217-289 tonnes

Sustainable Economics

Presently the system earns, through electricity sales, approximately GBP5,200 gross per year (GBP2,700 net after purchase of propane, grid power and maintenance costs), where is the UK pound. In addition the system provides electricity and heat to the house that would otherwise cost a further GBP2,500-3,500 for the same high level of comfort. Thus the total annual saving is about GBP5,700 per year.
 The battery of 60 series-connected lead acid cells may be charged at night using lower price grid electricity. During the day top-up charging is provided by the CHP unit. Charging may also be provided by the photovoltaic array, but this is dependent on the solar radiation intensity and the seasonal load. Excess wind power is sold to the grid during this period rather than being used to charge the battery because of the tariff arrangements.
 By making their farm virtually self-sufficient in energy, the Marmont family saves, on average, 34 tonnes/year of carbon dioxide emissions and almost 10 tonnes/year of fossil fuel.

Wind turbines

GBP 60,000

Photovoltaic panels

GBP 22,000

Batteries

GBP 15,000

Inverters

GBP 24,000

CHP unit

GBP 15,000

Control/monitoring

GBP 90,000

Legal/planning

GBP 30,000

TOTAL

GBP 256,000

For more information contact the CADDET UK National Team.

The CADDET Renewable Energy Newsletter is a quarterly magazine published by the CADDET Centre for Renewable Energy at ETSU, UK.

The articles published in the Newsletter reflect the opinions of the authors. They do not necessarily reflect the official view of CADDET.

Enquiries concerning the Newsletter should be addressed to
Pauline Toole, Editor, CADDET Centre for Renewable Energy, ETSU, Harwell, Oxfordshire OX11 0RA, United Kingdom. Tel: +44 1235 432968, Fax: +44 1235 433595.