Book - School of Science and Technology

Maintenance 679Table 23.12 Energy available from alternative sourcesFuelUnit ofdeliveryHeat content perunit of delivery(MJ)Solidcoal kg 28±30Oilkerosene (C2) litre 36.6gas oil (D) litre 37.9light (E) litre 40.3medium (F) litre 40.7heavy (G) litre 41.2Gasnatural kWh 105.5propane litre 0.095butane litre 0.122Electricity kWh 3.6Table 23.13 Carbon dioxide emission from fuels*FuelCO 2 emission(kg/kWh delivered)Electricity 0.44Coal 0.30Gas/diesel oil 0.25Natural gas 0.19* Values taken from BREEAM data.fuels; these rates will vary, and hopefully reduce, from time to time as the primary fuels usedfor electricity generation change and with increasing combustion efficiencies.Many of the other environmental issues arising from the subject of heating and airconditioningof buildings, such as ozone depleting refrigerants, water use and NO xemissions from combustion have been dealt with elsewhere in this book. To enable anassessment to be made of the impact that a building and its engineering services will haveon the environment, a rating system has been developed (since the early 1990s) basedupon a point scoring system known as BREEAM, the BRE Environmental AssessmentMethod. The issues that relate to building services include energy use, health and wellbeing,systems commissioning, water use and pollution. A number of publications on theBREEAM method are available from BRE.MaintenanceThere are various levels of maintenance which may be applied to building services, themost common being:. Corrective. The majority of operations are carried out on breakdown or fall-off inperformance, backed up sometimes with specific tasks undertaken on a regular basis.