My engineering has tended to be as alternative in the way I go about it as the systems I try to build. I have taken a different approach ever since my first job developing electronic systems for nuclear reactors. I got this position on the strength of samples of equipment I had been custom building and selling to my school friends. The cheerful, friendly working environment at this small company contrasted with its blinkeredness around the often suspect ethics of its projects. Aged 20, in 1977, I quit this enjoyable job to apply myself to the study of the science behind medicine, with the intention of making a more ethical contribution to civilisation. It didn't take me long to realise that I felt no more at home in this scientific, academic world with its cynical politics and economics. I got my degree, passed-up an irrelevant research opportunity and went back to electronics, but this time working for myself in the relatively benign but banal worlds of domestic and entertainment electronics: repairing, constructing and writing. Within a few years, my spirit could be constrained no longer and I broke out into art. Art, as ordered people know, is actually the expression of a psychological disorder, and my ordered persona was determined that I was not going to retire there entirely, yet. Thus the works on this page are those that have since come from about as deep in the right hemisphere of my brain as I can get.
Green electricity?
Whilst solar heating can be built from down-to-earth building components, solar electrical (photovoltaic, PV) systems are evolved from spacecraft technology. Though very common, the minerals silicon and aluminium used for PV panels are refined by extremely energy intensive processes.
Until recently, this "embodied energy" has been a significant proportion of the likely output of the solar panel, during its lifetime, meaning PV panels were only justfiably used in remote applications. This is how Weber and Blakers defined the situation at October 2003. The financial cost of conventional PV panels - which convert 7-20% of the energy of incident sunlight to electricity - is still a barrier to their full exploitation, as in many cases they will never pay back their capital cost, especially if a commercial loan is used to finance them.
More recently, with improved manufacturing and new concepts such as the Sliver™ Cell, just reaching production at the time of writing, these barriers are lowered.
Where relatively reliable wind-generated electricity can be purchased (link applies to the UK) from an already connected mains grid, this still offers a financial advantage over grid-connect solar PV. Nevertheless, economy of use through efficiency, and where heating is concerned - through improving thermal insulation, are by far the most advantageous first steps in energy cost and carbon emmission saving.
If you live in a remote, sunny place with no grid connection, fit a PV system even at considerable price disadvantage compared to a grid connection, at least to protect the landscape from degradation with more overhead power lines. A few PV panels power my encampment, when it is in sunny climates, and my second and third swimming pools; none of these have mains electricity. A simple audit of my own solar economics reveals that my panels will each need a minimum of 25 years to pay back their purchase cost, with many additional years to repay any investment in cables, controls, structures and batteries needed to operate them. As the batteries need renewing every 5 or so years, the system will never be more economical then a grid connection, even though the sunlight to power it is free.
Where I see solar "space" heating applied at all, I often feel alienated by its industrial rectilinearity. Planning regulations can actively discourage it through construction restrictions based on purely traditional or economic models. If I am in a building, I like it to respond to the weather outside and time of day: to feel like a sanctuary when the outside is challenging, to admit the outside and allow me to exit easily when outside is inviting; not to maintain a uniform environment as if the outside did not matter. In Spain, traditional architecture has small windows to keep the intolerable sun out in summer, with the assumption that electricity or bottle gas (LPG), or previously, wood - sometimes in this peculiar way, will be used to heat the rooms in winter. The possibility of selective and significant use of the welcome winter sun is precluded. Best by far designed into a building from the beginning, I would welcome an opportunity to show an organic, human approach to passive solar space heating. My favourite elements are small panes, thickly insulated shutters and "intelligent" shading.
Solar water heating systems are often simple to add-on, and work efficiently, collecting up to 70% of the sunlight energy incident on them, compared to the 10% that the best-engineered electrical panels will collect. They can be cost-effective even in a climate that is not renowned for its sunshine. One of the reasons I began living in Spain was to indulge my interest in developing solar water heating. By the time I had built several domestic-sized systems and one small hotel-sized system, however, I had realised that one major obstacle stands in the way of their more general acceptance - even in Spain: the relative subsidies on fossil fuel which remain in place so as not to rock the political boat. In any Spanish village, enough LPG will be delivered to you for 8 Euros to provide twenty or more, small hot baths or long hot showers, invariably burned in a 100 Euro boiler from which much of the heat doesn't even get near the water. Small wonder, those without idealistic motivations are not prepared to install reliable, effective solar water heating requiring an investment of upwards of a thousand Euros but likely to outlast its installer.
cheap solar hot water
In the late 1980s, I built my first solar hot water system for the Visitor Centre at Redfield Community, England, where I lived. Some of the components of a system had already been assembled, based on an early design of the Centre for Alternative Technology, Wales. I completed the system, but not as I would have designed it, along with installing much of the heating, plumbing and wiring for the Redfield Visitor Centre.
In Southern Spain, beginning in 1992, I built several systems from first principles. The ones I know of, with their original owners, are still operating. When I was first in Spain, anyone wanting to commission me to build solar water heating was used to taking a shower under a hose that had been lying in the sun: this warms and cools rapidly. No sun: no hot water. Strong sun: scalding water... illustrating that whilst a minimalist solar water system can be easily lashed-up in a sunny place, some intimate awareness of thermodynamics can help. I've had enough of building cheap and cheerful systems for other people but you might like to give me some encouragement to document how to build such systems, in these pages.
The image above-left shows an early system undergoing a rebuild. The recycled oil drum originally used for a heatstore was replaced with a custom built stainless steel one. The re-used steel radiator collectors were replaced with copper panels from an architectural salvage yard in England. Since the original build, the price of the corrosion inhibitor necessary for the oil-drum system has soared, while the cost of stainless steel has plummeted, in real terms.
One of the ways I scored over the 100 Euro ultimately-inefficient gas boiler, was to make solar water systems that would fill a bath in 5 minutes rather than the half-hour that such boilers took. Nevertheless, it was still necessary to continually remind potential investors of the amount of back-breaking lugging of heavy gas bottles they would be saving themselves with solar.
When Cortijo Romero began moving up in the world, in 1994, a few years after my first constructions in the vicinity had become known, I called in to chat with the new owner about alternative technology. Burdened by the customary debt from purchasing the property, the proprietor wanted improvements to be scheduled over several years. They were to coincide with the winter off-peak period that sun worshippers from the Far North did not think was a good time to be in Spain. This suited my migratory lifestyle perfectly, and we got down to business.
The first winter saw a three-pronged attack on the hapless, uncooperative and uneconomic plumbing of the place. Metres of corroding copper pipe buried in cold, concrete walls were replaced with a well insulated loop with a circulator, ensuring that hot water was usually at any hot tap instantly and without waste....
Several slow, electricity-guzzling hot water cylinders were sidelined and replaced with a landmark that became known to some as "Trev's Erection". This 5.5 metre high tower, stands among buildings that are all single story. The tower serves as a store for the heat collected by solar hot-water panels, sufficient for the hot water demands of the hotel for a day or so. It was originally conceived with the potential to store energy for space-heating as well. Potential, too, for a visual disaster, as are many modern solar installations? I tried my best to create otherwise: a Moorish folly which, if any visitor notices it, probably adds something to the ambiance, and constructed in the embrace of a fig tree, on a concrete raft to protect it from the roots. Within its outward inkeepingness, it contains some successful, shot-in-the-dark technology. It is the only ferrocement hot - like 70 to 90°C hot - water storage tank that I know. It is twin skinned, with 20 cm of insulation, a reflector and all the pipework concealed between the skins. Within the tank are three sets of heat exchanger coils for the domestic hot water, enabling progressive heating of the water to the required temperature with minimum loss of store temperature. The heatstore is also probably the most cost effective built to such a specification!
My main sub-contractor on the tower took payment in the form of a complete low-impact domestic solar hot water system which I built for him (see above). His labourer traded LETS with me for a solar water heat store which I prefabricated for his own installation. This first season's work at CR was sewn up with the construction and fitting of four of the full complement of twelve solar panels, plus a condensing gas-fired boiler. The boiler was bought in the UK, as no suitable boiler could be sourced in Spain at the time. Such boilers were in their infancy and were developing a bad reputation for reliability amongst installers. This one was indeed beset by problems. The original solar collectors were all built by hand, partly to provide work for local people, and partly because the price of commercial collectors could thus be undercut by a large margin.
Along with many fittings, the normal, mild steel, flat-panel heating radiators that were to be used as cores for the collectors were purchased from England. Central heating components, especially compression fittings were relatively esoteric and hence costly, if available at all, in the area at the time. The heating radiators were coated with selective absorber material and mounted in specially designed, farmed-soft-wood enclosures, to be treated annually with linseed oil - not a problem on an easily accessible roof. See the illustration at the top of the page. During the next year's winter and spring, more panels were installed but the ultimate number of panels was reduced in order to minimise interference with the view from the dining room, which looked out over the building with the panels on the roof, to the mountains beyond.
This reduction in panel area meant that my hope of collecting enough heat in the spring and autumn to contribute to the space heating of the rooms was no longer realisable. Meanwhile, in the cramped space beneath the floors of the building, custom made underfloor heating panels were installed. The difference to the previously inhospitably cold floors and general comfort of the rooms was remarkable. This link goes on about the virtues of underfloor heating. In the rooms that could not practically be fitted with underfloor heating, large, non-convector flat panel radiators were installed, to run at the same lower temperature compatible with obtaining the greatest possible efficiency from the condensing boiler and heatstore. The same underfloor heating link expands on this.
With the proposed construction of a new suite of rooms for the expanding Centre, I did my best to influence the specifications towards energy conservation and carefully engineered comfort. I succeeded totally with the installation of the underfloor heating and pumped-loop hot water... partially with persuasion to install suitable room insulation - one third of the thickness of 10cm I recommended was installed... and hardly at all with my proposals for a seasonally-tuned passive solar gain architecture. The final season of actual installation work concluded with the custom built telemetry and control systems for the monster. Subsequent to the actual installations, some weeks were spent writing an 85 page operating and fault-finding manual for the system, of the kind I provide for any project when I am permitted(!) The final chapters for the manual were compiled from a camp at over 2000 metres altitude in the Sierra Nevada natural park, in a spot now closed to vehicular access. The camp was to take full advantage of the long hours of summer sunlight on the solar panels, powering the computer and printer as well as all else, all day, plus the refreshing, thought-clearing coolness of the air (and walks in it) compared to the 35°C fug around CR itself, in the valley below....
a definition
Sometimes referred to as "co-generation", combined heat and power means the use of the otherwise waste heat from a thermal process being used to generate electricity. Internal combustion engines can have their cooling and exhaust heat reclaimed. Fuel is saved if electrical heating can be replaced with otherwise waste heat. Heat is more difficult to move long distances than electricity, without uneconomic losses, so CHP tends to be tailored for neighbourhoods or single users. CHP is also more technology intensive and needs more attention than equivalent heating systems running alongside a mains electrical installation. But when I undertook to become self-sufficient in energy at my camp in the Sierra Nevada mountains of Spain, I knew it was time to give this project a high priority. Originally developed on an industrial scale, the term "micro" (μ) refers to the relative size of the kind of unit I am working on.
CHP systems in the power range that I was looking for just did not exist when I began this project in 1996. I still only know of one range targeted for domestic use, slowly moving towards production. I was looking for an electrical output of about 5 kilowatts - enough to run a small workshop including a welder - and about the same heat output as a small domestic central heating boiler - about 12 kW. So I began looking for sources of suitable components to assemble my own. Finding an economically sized engine to power the unit was the first hurdle. This drew a blank on one account alone: nearly all engines of such power output were air cooled, and air cooling is difficult to reclaim the heat from. In the end, I abandoned my search and purchased an ex-demonstrator 5kW air-cooled Honda-powered generator and did my best to reclaim the heat from that.
First of all, I converted the petrol engine to run cleanly and more economically on bottled propane/butane gas. As I am easily upset by air pollution, this was a high priority to me. The exhaust from the engine burning gas has a very mild, inoffensive smell, and several deep breaths of it have no noticeable effects on me compared to immediate nausea caused by the slightest inhalation of its fumes when it burned petrol. Gas fuelled engines themselves also remain cleaner and experience less wear than engines run on carbon-rich fuels.
Next I built a prototype exhaust heat exchanger based on my experiments with wet heat-exchangers for solid-fuel-burning appliances (see below), with modifications to accommodate the greater volume and pressure of an internal combustion engine exhaust. A ducting system was built from the engine and alternator cooling air exits to an air-to-water heat exchanger. Finally, the unit was built into a weather-proof, sound-insulated cabinet. The unit was tested briefly before leaving the UK for Spain, and results were encouraging. The first real test of the unit came when I reached the Pyrenees. Winter had begun, and I made the bad choice of spending a night in a very scenic but very exposed place, high in the mountains. The photo on the right was taken there. The results of this mistake included some serious damage to the CHP unit and van due to deep-freezing!
This freezing episode was a lesson to me to reduce the complexity and vulnerability of my CHP system. I discarded the heat reclaim from the engine and alternator cooling air and built a simpler, much more robust stainless-steel exhaust heat exchanger - see the photographs. The zig-zag fin exhaust path was then welded into an outer vessel containing the heat transfer fluid. The heat-transfer capabilities and robustness of this exchanger were good but it was not as effective as a silencer as the wet system had been. As it still functioned as a condensing heat exchanger, care had to be taken with the subsequent routing and silencing of the exhaust, as it included a steady trickle of slightly acidic water.
The generator with its exhaust heat exchanger acting effectively as a small central heating boiler was then attached to a carefully positioned and insulated system of hoses around my camp site, connecting it to a domestic hot-water heat exchanger and heatstore with a 3kW immersion heater, and demountably, to my van heating. This system could also accept heat from a solar water-heating panel. The CHP unit typically powers or heats my workshop and van, giving lashings of effectively free hot water, enough to fill my hot-tub after an hour's use. Much of the time, however, even this 5kW (electrical output) CHP unit is excessive for the heat and power needs of my camp, especially when solar heating and power are not available but no substantial power demands are being made.
I am working on an even smaller, complementary, more efficient CHP unit to conserve gas during times of extended small power demand. This unit is based on the relatively new generation of clean, quiet, four-stroke, water-cooled motor-scooter engines. Electrical output is from a high-power (1 kW), low-cost, 12V automotive alternator, ideally matched to the lighting and battery charging loads of this complementary, low-energy use scenario. The engine has electric start and I have already fitted it with an appropriate gas conversion. The engine and exhaust heat are transferred to the same heating/cooling circuit as the van and larger CHP system. Additionally, this unit also drives, via the normal electrical clutch, a heat pump in the form of an automotive air-conditioning compressor. This will be used to provide efficient air-conditioning for the van or workshop.
This second CHP project is presently stalled due to a spare parts issue: the Yamaha "Majesty" power-unit, cost-effectively removed from a write-off scooter, developed a faulty electronic ignition module; it is a unique, specialised module, and a new replacement would cost more than the whole used engine, and breakers seem unwilling to sell the module separately at reasonable cost. Perhaps, if you can help, you could email me. Pending getting the engine running again, is also the issue of a speed governor for the engine, which unlike the first CHP unit, does not have such a device built-in.
My editor admonishes me, but I have not written this yet. Some practical details intercede.... Sorry.
pollution issues
bubble wet heat exchanger
redfield tests - photo
current project - photo
Finally, one of my most rustic and rusty works, this lash-up "appliance" which also worked superbly! The low-tech design, using small, mostly free, flat mirrors was loosely based on very high-tech installations nearby in the eastern French Pyrenees. (See this Ephemera page for two images). The high altitude and clear skies here mean regular, strong sun. Two nearby solar furnaces are open to the public, one being the largest of its kind in the world, covering a complete mountainside! They have produced the highest temperatures ever recorded in furnaces - using "nothing more" than arrays of mirrors controlled by computer!
My humble creation is remarkable in that it was built almost entirely out of scrap materials in a couple of days. The frame was built from pine saplings thinned from a nearby plantation. The only specially purchased part of the device was a 1.2 metre square mirror. The oven itself was an old metal cabinet lined with 100mm glass-wool insulation and tiles, with a piece of cling-film for a front. The film worked better than an old glass oven door, as it blocked less light and kept the heat in well enough - though it did have a tendency to split easily when hot and need replacement. I recorded temperatures of well over 100°C in my oven and was able to cook potatoes and cakes.
The oven was designed to be as easy to use as possible. With no tracking mechanism, it had to be turned slightly every half-hour, to maintain temperature. This was not a problem for cooks, needing to check how their work was going about that often, anyway. To this end, the whole assembly turned easily on a single post in the ground. Regulation was simply keeping the patch of intense light on the door in about the right place. The large mirror was adjustable for the height of the sun. This does not vary much during the middle of the day when the oven is best used for cooking. The small mirrors, seen from the back in the photo, are all prefocused on the door and need no routine adjustment.
The downfall of the oven was simply that the nearest sunny place to the kitchens was about 30 metres walk, and busy cooks wouldn't pre-cook food in the middle of the day, walk the distance, or get to know the appliance. A slightly bigger mirror would have made the oven quicker to heat and compensated for less sun.
![CRpanels.jpg](javascript:win3s(365,513,40,"images/!LARGE/","#ffffff","CRpanels.jpg","the author cleans panels described below © Trev Miller 2004","noblurb");)
![PeterSolarProgress.jpg](javascript:win3s(574,431,40,"../ephemera/img2002.11/!LARGE/","#002050","PeterSolarProgress.jpg","the hat insulates; side insulation not shown; built for one wizzard by another; © Trev Miller 2004","noblurb");)
![TrevorSolar.jpg](javascript:win3s(609,463,40,"images/!LARGE/","#ffffff","TrevorSolar.jpg","TrevOR and his new system © Trev Miller 2004","noblurb");)
![CR_courtyard.jpg](javascript:win3s(655,467,40,"images/!LARGE/","#ffffff","CR_courtyard.jpg","have you been there? © Trev Miller 2004","noblurb");)
![CRTower.jpg](javascript:win3s(388,600,60,"images/!LARGE/","#ffffff","CRTower.jpg","completed before the fig tree put out its leaves © Trev Miller 2004","noblurb");)
![CR_tower_insulation.jpg](javascript:win3s(693,475,40,"images/!LARGE/","#ffffff","CR_tower_insulation.jpg","ve have vays and means of making you understaand © Trev Miller 2004","noblurb");)
![CRtowerTub.jpg](javascript:win3s(800,600,0,"images/!LARGE/","#ffffff","CRtowerTub.jpg","1994... before the addition of corrosion inhibitor! © Trev Miller 2004","noblurb");)
![CRteam.jpg](javascript:win3s(800,600,0,"images/!LARGE/","#ffffff","CRteam.jpg","my collector panels and underfloor heating team (the heating panels are leaning against the wall of the group room in the background)","noblurb");)
![CR_schematic.jpg](javascript:win3s(557,658,20,"images/!LARGE/","#ffffff","CR_schematic.jpg","Cortijo Romero heating system schematic overview - © Trev Miller 1997","noblurb");)
![Mont_Louis.jpg](javascript:win3s(797,535,40,"../2d/images/!LARGE/","#f6f6f6","Mont_Louis.jpg","picturesque fort with Pic du Canigou in distance © Trev Miller 1999.03.25","noblurb"))
![133gennyHtxFolding.jpg](javascript:win3s(503,375,0,"images/!LARGE/","#000000","133gennyHtxFolding.jpg", "engineering or sculpting? © Trev Miller 2004","noblurb");)
![145gennyHtx.jpg](javascript:win3s(503,375,40,"images/!LARGE/","#666666","145gennyHtx.jpg", "exhaust heat exchanger trial fit without water jacket © Trev Miller 2004","noblurb");)
![solar_oven.jpg](javascript:win3s(424,600,50,"images/!LARGE/","#d0ddff","solar_oven.jpg", "backs of half of the concentrator mirrors to the right © Trev Miller 2004","noblurb");)
