This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
Thanks for taking the time to post more details about the modern micro-generator CHP plant. That study sounds interesting. Is there any way of obtaining a copy, if its a government document covered by the official secrets act I probably still have the necessary security clearances to see it!
I'd be particularly interested to see how it was proposed to get round the efficiency problems inherent to the wide output load range which a single dwelling CHP needs to cover. Everything from one light on at mid summer midnight (possibly LED these days) to full heat and full power on a freezing mid-winter evening. Far too great a range to be covered at anything like optimal efficiency by a live running plant. Even at optimal efficiency the savings relative to grid supply aren't that great so it becomes important to ensure that efficiency is high under as much of the load range as possible. Not an easy task especially as most of the time demand will be in the lower output regions so optimisation for low output reduces efficiency at higher output where more fuel (and costs) are consumed.
The engine generator combo described is interesting. Are there any published performance figures for it? I presume a prototype was built. I'm sure its only the space constraints of a forum reply which makes the description sound contradictory.
In particular your reference to continuous combustion and Atkinson cycle is strange. Generally the Atkinson cycle refers to intermittent combustion engines where asymmetry between compression and expansion phases is introduced to increase system efficiency. Ideally the modified cycle is used whereby the degree of asymmetry can be varied conferring most of the benefits variable cut off gives the reciprocating steam engine. Not the least being the ability to size an engine to run with high efficiency where only a moderate output is needed whilst having over-driving capability when maximum output is needed. This of course was the thrust of Prof Timoneys work on the TS3 engine. There is a good deal of interesting, but unlikely to be practical, stuff on rotary Atkinson engines on the Internet. Sliding members in the combustion chamber, they have gotta be joking!
If it wasn't for the mention of 12 V battery and Dyna-start I'd have said that, given the costings and proposed design to production lead, time your description sounds like a mono-tube boiler (flash) steam engine system. Which is the way I'd do it. Not least because that concept does at least get round the heat/power mismatch problem as direct connection between boiler and a conventional heating system can be arranged when power generation needs don't produce enough heat. I guess the Atkinson bit could refer to a variable number of stages on the expansion side. Easily done with a double acting triple expansion reciprocator, optimising valve gear cut-off variation switching and number of stages employed against load sounds a nice post grad problem! Not quite so easy with a multi stage turbine but still possible.
Common bearing and clutched quill shaft is an odd way to drive the generator. End on drive via coupling is easy and cheap besides being far more convenient at service time. Given you want AC output a constant speed drive makes a lot more sense. High efficiency over wide speed range is not a normal generator characteristic. Presumably this was a de-costed 400 Hz design as satisfactory single phase can then be got with fairly simple circuitry. High generator speed also allows flywheel energy storage for spin up / coast down cycle so the prime mover doesn't have to run continuously at low output.
However you do it this beast is going to be much, much more complex than a condensing boiler so I still find it hard to accept your costs. In particular my professional experience as a scientist/R&D engineer make me leery of accepting the outcome of any pure paper studies. I've been bitten on the backside too often by the real world not behaving the way the most eminent authorities claim it should do. I've also seen these high powered committee studies miss the blindingly obvious, usually out of enthusiasm for novelty or neatness, on several occasions. Explaining practicalities to an assemblage of PhD's buttressed by pages of mathematics can be difficult.
Thank you for your interesting insights into prime mover and generator design. Before I comment on your Post, I would reiterate my original purpose: to draw attention to the dreamworld pronouncements of politicians, bureaucrats and unfortunately academics, who really should know better. Dave kicked off the discussion without mincing words, as the “daft idea of micro-generation”, I followed with a supporting Post which drew on my industrial experience to make two points in one example. First , Dave seemed to support his comments, by drawing our attention to the pre-war establishment of our national grid with the inevitable consequences of a state run electrical power industry. Yes, they halved coal consumption, but the built in bureaucratic management inefficiencies actually increased the cost to the consumer. (I know this because my Father lived through the changeover).
So, my first point highlighted the fact that private industry, if left alone, will always out-perform state industry, and my second point was that the state never willingly relinquishes regulatory powers over major utilities. My reference to the DTI programme was, (unfortunately). I did say that it was an 'exercise', but the real exercise was to prove to industrial interests that they would be ill advised to 'take the Queen's shilling', even if it was offered. It wasn't, because we refused to accept the DTI's onerous contingency clauses, do it by numbers routine, jump through these hoops, quarterly technical and financial audits, ad (sickening) infinitum!! As it was, the DTI were the losers, (of taxpayer's money); all of the schemes that they backed were abortive. CHP is still very bad news for bureaucrats today, they have very long memories: politicians don't, which is why they never learn.
My comment on your Post Clive:-
Frankly, the technical questions that you raised and some of which you rhetorically answered, are totally inappropriate on a public forum. Professionally I could see your questions as a 'fishing expedition', but as you describe yourself as a “professional scientist/R&D engineer”, I assume that you adress the technology of CHP from an academic viewpoint. This is a mistaken pursuit, for there is no common ground between applied technology and academia. Especially in the R&D of private industry,
the language, the motivation, the skills, and the rewards are radically different. For example, the official secrets act: government agencies can never get their heads around the fact that when they seek to engage industry in collaborative funding of R&D, uppermost in industry's mind is to protect their knowledge base from industrial espionage. In the market place, Patents are Crucial. Making what are, in effect, Prior Disclosures to civil servants is a very risky business, despite their assurances of confidentiality, it is a leaky sieve!
So Clive, if you wish to satisfy your curiosity about my industrial activities, please e-mail me privately with your 'commercial' need to know particulars as most of the answers to your technical requests are not in the public domain, and some of the research is still extant, but moved into different fields. In the meantime, would you care to apply your obvious scientific mind to the other rubric of the Conservative Party's Policy Review Committee in the Guardian article on micro-generation:-
Chairman Oliver Letwin spouts thus: based on David Cameron's promise of 1 million units in place within 10 years, “Our costings suggest that by 2020 ---- they could be producing 2GW of electricity. (Big deal, 2 billion/1 million = 2,000 watt hours, say worth 25p!). Then he says that two-thirds of energy used in power stations, “is lost in the wires that transmit it”. (Go to the 'horses mouth', the National Grid transmission losses are between 12 and 14%). Finally, they expect to see mass-market finance packages available on the high street! Do I exaggerate when I say 'Dreamworld'?