Fundamentals: Long term fuel for the future

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- CommentAuthorrenewablejohn
- CommentTimeAug 10th 2012
Posted By: SteamyTea
Posted By: renewablejohnYour making the classic error of starting with an annual fuel consumption and then trying to fulfill that consumption with a single fuel in this case wood

Hardly a classic error, just highlights the difficulty of a single fuel.
Not really valid to use brought in waste as that has to come from somewhere and will have an associated land area connected to it.

I hardly see how using garden waste in a composting toilet will reduce my energy usage to 5%, have I missed something?

You have missed the point. In a well insulated home 90% of its energy needs can be obtained from a solar thermal oil application leaving a 10% shortage which can easily be filled by biomass. What I am suggesting is your number 2's are a forgotten form of biomass which can be utilised to reduce your overall biomass requirement down to 5%. As for bought in waste it is better to recycle to reduce your own energy needs then use more energy in moving to a land fill site.
- CommentAuthorJTGreen
- CommentTimeAug 10th 2012
You mean when make the sensible decision to keep the fossil fuels in the ground?

A mix of renewables - solar, wind, wave - some 'green gas' (from anerobic digestion), small scale domestic biomass from sustainable sources (coppice, managed woodland), some next generation nuclear, recycling nuclear waste but above all absolutely masses of negawatts in every aspect of life. New generation of wind-powered ships for sea freight. Massive increase in cycling, including for small freight from urban periphery distribution centres. Electrify as much as possible. Reduce the number of airports.

When I think how much our hospital uses in resources - the single use items (for infection control purposes), the space heated and lit, the masses of technological kit, the numbers of staff, patients and visitors traveling long distances to a regional centre .....a post-carbon future is going to be very harsh and make a lot of changes. I predict they'll be more focus on primary health care and some very harsh decisions made in acute medicine.
- CommentAuthorfostertom
- CommentTimeAug 10th 2012
Posted By: renewablejohnIn a well insulated home 90% of its energy needs can be obtained from a solar thermal oil application
Are we talking space heating and/or DHW and/or electricity?
- CommentAuthorrenewablejohn
- CommentTimeAug 10th 2012
<blockquote><cite>Posted By: fostertom</cite><blockquote><cite>Posted By: renewablejohn</cite>In a well insulated home 90% of its energy needs can be obtained from a solar thermal oil application</blockquote>Are we talking space heating and/or DHW and/or electricity?</blockquote>

Talking space heating, DHW and electricity. Thermal oil technology is moving fast in the commercial sector with bread ovens and laundry applications already well established. Based on the thermal oil bread oven technology if applied to the domestic market will result in cookers and hobs being heated directly with thermal oil in addition the instant steam facility will make the electric kettle redundant and instant steam pressure cookers will become the norm. Thermal oil laundry applications already include washers, dryers and ironers. Once all these major electric heating elements are taken out of the electric equation the small remaining electrical requirement can be achieved by using thermal oil TEG's the hot side being 230C and the cold side 30C which is just the right temperature required to run your UFH. A simple thermal oil heat exchanger takes care of the DHW. Heating of the thermal oil achieved by the use of standard Ritter high temperature thermal solar tubes with backup via a Dunsley Yorkshire biomass boiler. Key to the system is a thermal oil flask so that high temperatures can be stored for long periods of time and is extensively used in the Asphalt industry.
- CommentAuthorfostertom
- CommentTimeAug 10th 2012 edited
You're reminding us of what you've described before. Interesting, maybe impressive. Particularly non-electric direct-heat cooking/washing; elimination of those big loads (which Passivhaus etc relies upon!)

The oil is heated in solar collectors? What about the bugbear of solar thermal collection, when in deep winter, outside scenery and sky is so cold that the collector panel gets cooled by re-radiation as fast as it adsorbs insolation? Would you be relying on vacuum/heat pipe collectors to minimise re-radiation loss? At the same time generating exceptional flow temp? What about the minute-by-minute intermittency of winter insolation, as clouds pass the sun, which puts a high proportion of the collection time into standby loss/startup lag mode? What deep-winter collection efficiency % are you hoping for? I trust that you're not relying on the Dunsley biomass boiler to do nearly the whole job in deep winter? If so, then IMHO that's the downfall of the whole idea.
- CommentAuthorrenewablejohn
- CommentTimeAug 10th 2012
<blockquote><cite>Posted By: fostertom</cite>You're reminding us of what you've described before. Interesting, maybe impressive. Particularly non-electric direct-heat cooking/washing; elimination of those big loads (which Passivhaus etc relies upon!)

The oil is heated in solar collectors? What about the bugbear of solar thermal collection, when in deep winter, outside scenery and sky is so cold that the collector panel gets cooled by re-radiation as fast as it adsorbs insolation? Would you be relying on vacuum/heat pipe collectors to minimise re-radiation loss? At the same time generating exceptional flow temp? What about the minute-by-minute intermittency of winter insolation, as clouds pass the sun, which puts a high proportion of the collection time into standby loss/startup lag mode? What deep-winter collection efficiency % are you hoping for? I trust that you're not relying on the Dunsley biomass boiler to do nearly the whole job in deep winter? If so, then IMHO that's the downfall of the whole idea.</blockquote>

If you look at the Ritter high temperature collectors you will notice that there vacuum tubes so re-radiation is not such a significant problem. Also the tubes are designed with reflectors to achieve higher temperatures which linked to a temperature controlled variable speed pump allows high temperature thermal oil input even on overcast days. In deep winter I am assuming at least one nice day per week but if all else fails the Dunsley has the capacity to keep the system running and will modulate depending on tank temperature.
- CommentAuthorfostertom
- CommentTimeAug 10th 2012
Posted By: renewablejohnvacuum tubes so re-radiation is not such a significant problem
But how significant still - that's the question.

Posted By: renewablejohnwith reflectors to achieve higher temperatures which linked to a temperature controlled variable speed pump allows high temperature thermal oil input even on overcast days
Agreed, that's normal principles for warmer days when re-radiation loss isn't a killer - but the hotter you're trying to collect, by any means, the fewer days you'll succeed. It's easy in summer - the question is, how far back into the colder months can you rely (as you propose) on copious execptionally-high-temp collection; how soon do you have to resort to the boiler?

Even if you can collect very hot, % efficiency of collection plunges as the set flow temp rises. You'll collect more heat on any day, if content to take it at lower flow temp.

Posted By: renewablejohnIn deep winter I am assuming at least one nice day per week
That can be determined for ea site by study of historic weather data. But what's a 'nice day'? X amount of insolation uninterrupted from a clear sky is very different from same X amount of insolation heavily interrupted by intermittent clouds etc (typical of winter). With intermittency, standby losses and startup lags can dominate. Available weather data doesn't provide that crucial detail. You have to assume the worst and optimise to minimise standby losses and startup lags.

In fact really significant extension of solar usefulness (beyond well established spring/summer/autumn DHW and PV) depends on ruthless optimisation for mid winter. If the solar system can't fully hack mid winter, then you're back to paying for two systems - solar and conventional (pref gas, failing that biomass) boiler.
- CommentAuthordjh
- CommentTimeAug 10th 2012
Posted By: renewablejohnThermal oil technology is moving fast in the commercial sector with bread ovens and laundry applications already well established. Based on the thermal oil bread oven technology if applied to the domestic market will result in cookers and hobs being heated directly with thermal oil in addition the instant steam facility will make the electric kettle redundant and instant steam pressure cookers will become the norm.

John, That sounds interesting. Do you have any links to descriptions of the commercial systems and/or to any proposed domestic system?
- CommentAuthorSteamyTea
- CommentTimeAug 10th 2012 edited
Having studied the frequency of cloud cover, and slowly working my way though a years worth of curve matching to determine a baseline, all I can say is that with a mean of 14 Wh/m^2 of resource and a demand of 19 Wh/m^2, I am going to struggle, and that is before entropy losses.
Now if I owned a farm with dozens of acres, that would be a different story, but I would be denying someone else access to the 'free resource'
All the 'oil' does is allow a higher temperature to be transferred (compared to water), not any more energy, that is governed by collector surface area and efficiency.
- CommentAuthorfostertom
- CommentTimeAug 10th 2012
Posted By: SteamyTeaAll the 'oil' does is allow a higher temperature to be transferred (compared to water), not any more energy, that is governed by collector surface area and efficiency.
And other things being equal, higher collection temp (transfer temp) means lower collection efficiency, hence less energy collected, albeit at higher (perhaps more useful for some purposes) temp.
- CommentAuthorfostertom
- CommentTimeAug 10th 2012
Posted By: SteamyTeaHaving studied the frequency of cloud cover, and slowly working my way though a years worth of curve matching to determine a baseline, all I can say is that with a mean of 14 Wh/m^2 of resource and a demand of 19 Wh/m^2, I am going to struggle, and that is before entropy losses.
There's always gold nuggets in there - but so obscure!

Great that you're studying frequency of cloud cover - as it's not an on/off thing, clear sky alternating with heavy cloud, but shades of on-ness and off-ness ... well, how do you quantify that?

Will you be able to quantify the ratio of continuous collection time, to continuous non-collection time, to that intermediate state where collection is dominated by shutdown/standing loss and by startup lag?

What's that about curve matching?

Does the foregoing have direct bearing on your demand of 19 vs supply of 14, or is that a separate parallel observation?

Entropy - great stuff - but how does that come into it. I'm sure it does, but give us a clue?
- CommentAuthorSteamyTea
- CommentTimeAug 10th 2012
Posted By: fostertomwell, how do you quantify that
W/m^2 on the ground, that is the easy bit.

Posted By: fostertomWill you be able to quantify the ratio of continuous collection time, to continuous non-collection time
Did that a year or two back, not that hard, you may remember that I said you can use about a third of the light energy available for ST, well I am just refining that.

Posted By: fostertomWhat's that about curve matching?
The azimuth and altitudeof the sun follow the sum of sine waves, for a clear sky scenario, that I am slowly doing is breaking down the daylight hours into chunks and seeing what is going on and then matching the temporal frequency distribution to a sum of sine waves. That is the slow and very tedious bit.

Posted By: fostertomDoes the foregoing have direct bearing on your demand of 19 vs supply of 14, or is that a separate parallel observation
None whatsoever, that are just mean figures for where I live and what I use. Just highlighting the problem of using solar as the only energy source.

Posted By: fostertomEntropy
Flanders (Stephanie's Dad) and Swan have a song about it. Nature wants to settle in the lowest energy state and happily goes there, to reverse that, i.e. heat a house up in winter or raise the temperature of water, requires a lot more energy than you actually need, it is why biomass is not really a very good energy source, takes a horrendous amount of sunlight to un-bond hydrogen from oxygen and carbon from oxygen and recombine it as hydrogen and carbon, much easier to do it with PV and a bucket of salty water.
- CommentAuthorWillInAberdeen
- CommentTimeAug 10th 2012
Posted By: fostertomEntropy - great stuff - but how does that come into it. I'm sure it does, but give us a clue?

Posted By: fostertomAnd other things being equal, higher collection temp (transfer temp) means lower collection efficiency, hence less energy collected, albeit at higher (perhaps more useful for some purposes) temp.

answered your own question there Tom!
- CommentAuthorfostertom
- CommentTimeAug 10th 2012
Posted By: SteamyTea
Posted By: fostertomWill you be able to quantify the ratio of continuous collection time, to continuous non-collection time
Did that a year or two back, not that hard
No, that's the easy bit - my point was about their ratio to the third state
Posted By: fostertomto that intermediate state where collection is dominated by shutdown/standing loss and by startup lag?

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