Book - School of Science and Technology

Conclusion 701Typical electrical outputs are in the range 0.5 to 3 kW at an electrical efficiency ofbetween 15 and 25%. Heat to power ratios vary in the range 2.5:1 up to 4.5:1.This type of CHP unit is anticipated to be used as a direct replacement for a conventionalgas fired domestic boiler. Operation of such units will therefore differ from conventionalCHP in that operating hours may be relatively low and electrical productionmay not match demand. Connection in parallel with the electrical grid will therefore beessential to absorb excess power and to supply any power short falls.ConclusionThe introduction of small scale,single site,CHP systems as described in this chapter* is aconsiderable advance upon the grandiose proposals advanced in the recent past. Theseventh edition of this book referred to projects of the magnitude then envisaged andoffered the opinion that they were doomed to failure. Hindsight confirms that there wastruth in the paragraph which ended that edition:The more sensible alternative lies with the large number of relatively small industrialestates and science parks throughout the British Isles,each having access to real `handson'experience of heat and power generation. Encouragement of properly engineeredexercises on this scale,where high quality construction of the heat distribution systemwill not absorb a disproportionate cost,would be more productive than a greaterexpenditure upon grandiose cost-limited white elephants. Real energy savings wouldresult,industrial competitiveness would be improved and return upon capital expenditurewould be available rather than a long term bad debt. Small,in this context,is financiallysound as well as beautiful.*For further information on this subject,the reader is referred to the many excellent publications by theEnergy Efficiency Office Best Practice Programme and CIBSE Applications Manual 12.