Wednesday, September 3, 2008
Using Windmills to Heat Water? The problem of urban energy storage...
One of the arguments I make in my thesis is that current urban planning assumes a "sites and services" approach to development that relies on a "plug and play" solution to service provision. I argue that the "plug and play approach" to urban housing design forces us to build "leech-like" dwellings that must plug into State controlled energy and water pools. (Please note that I am not against designing dwellings for the plug and play ease of using solar modules or small wind systems -- we should differentiate between decentralized plug and play and centralized plug and play -- it is the latter I am against.) A centralized plug and play service approach, I argue, creates dependency on external suppliers and puts consumers, particularly the urban poor, in a dangerous situation when market volatility or market manipulation suddenly raises prices of the vital inputs we depend on (consider the case of Enron and the rolling blackouts of California that hurt all the urban poor families in Los Angeles with the notable exception of our colleagues Al Silva and Ramon Navarro at our Solar South Central NGO, where the lights never went out !).
Developers are obsessed with an infrastructure of "pipes and cables" connecting the household, with its myriad appliance and consumer goods, to the water and energy "utility provider". We planners rarely think through the benefits of full decentralization, deregulation, and distributed generation, usually paying mere lip-service to the general idea of a diversified portfolio of planning solutions in a free market without asking what a truly free market, in which there are no barriers to entry and everybody can be both producer and consumer, might look like.
I argue that we don't take the notion of the "prosumer" seriously enough, particularly in the third world, even though semi-peasant/semi-proletarian urban residents have defied the logic of Capitalism for a century, while helping resolve its paradoxes and subsidizing its exceesses through home production. Despite the benefits to Capital of self-exploitation and petty commodity production and household reproduction through self-provisioning, many planners still have "Le Corbusier" style dreams of turning housing for the working class into a mere machine for living, hooked up to a grid that reinforces the power of the powerful.
The development status quo is a linear, hierarchical model that favors centralization of power, both on a physical and political level. So most urban planners tacitly ignore or marginalize literature that speaks of "radical solutions" that would enable urban households to "prosume" -- to use the household to both produce and consume at the same time. Zoning laws, in fact, prohibit most productive activities in "residential" areas.
This is changing in up-scale enclaves, however, particularly in progressive places like Germany and California and Spain where not only are people encouraged to take advantage of "nature's subsidy" to self-provision by installing solar heaters, photo-voltaics, geo-thermal heat pumps and small wind-turbines, but where feed-in-tariffs encourage household production of energy on a commercial scale and the ability to "spin the meter backward" lets prosumers sell power to the grid.
I have been thinking a lot about how to make households in Cairo able to participate in gaining the benefits of this international change of attitude so that if the ruling regime ever allows it, urban residents will be ready to make their contribution to their Nation's challenges. I've also asked myself "how can each household make best use of the environment surrounding it?". In most of the areas Solar CITIES works in we are blessed with abundant sunshine and low-rise real estate, so solar hot water systems and photovoltaics have been the logical solution. It would be easy to conceive of installing grid-intertie capacity to PV systems in the city if the government permitted it. Small scale wind turbines could also serve to pump electrons into the common electron pool.
But what do we in the interim, during these rough days when the Egyptian government and planners are turning a blind (if not baleful) eye to distributed generation?
The problem with PV and home-scale wind power in cities without grid-intertie permission is the old problem of "how to store useful quantities of energy"? Egypt's National Renewable Energy Authority published a Country Study with UNEP in 2001 in which they concluded that "consumers are not satisfied with the power obtained from PV" (p. 40). The perception that PV cannot provide high power levels comes from stand-alone systems with limited battery storage -- I can assert from my own off-the-grid experiences that once I had 8 deep cycle batteries in my apartment for storage, my modest 1.2 KW Solar Array was able to provide plenty of juice for my refrigerator, microwave, computer, lights, water pumps, electric guitars, Television, fan and even an airconditioner (for about 2 hours each sunny day). The current and available amp hours were dependent on the battery bank.
I looked at my battery bank as my savings account and my solar panels as my income source. Obviously if you spend very little and save up a lot you can make big purchases once and a while, and by analogy you can power your whole house for one day with the "savings" produced from the stored income of a single solar panel if you wait long enough. Thus the PV panels are not the limiting factor. My system grew from a mere two 75 watt panel small system to a mix of 14 100 Watt and 75 watt panels over a period of two years. My battery bank grew from a single pair of 6 volt Trojan L-16 deep cycle batteries to four pairs of batteries. But it was the battery bank that mattered when I needed full power.
The problem in Egypt is not only that PV panels are so expensive, costing between 8 and 10 dollars per (uninstalled!) watt -- 3 times the global market price -- due to markups, import duties and taxation. Even when UNEP and GEF and other agencies completely subsidies the PV panels for small scale demonstration projects people are dissatisfied because it is almost impossible to obtain good deep-cycle batteries, and the few that are available are also at least 3 to 4 times the free market price.
With no grid-intertie option, consumers are severly constrained by the amount of useful energy they can store and use. This same problem applies to small scale wind power.
Egypt's renewable electricity situation resembles a country where it rains pennies from heaven but people can only collect this "manna" in a single gallon-sized piggy bank. How can you amass any capital when the size of your savings account is severely limited?
Even the impressive 10 KW AC Desert Development Center (DDC) solar array, installed by the American University in Cairo back in 1981 to power the centers headquarter near Sadat City (see Adli Bishay's reminiscences of this failied Hassan Fathy "housing for the poor" experiment), and the additional 3 KW DC water pumping system, sat unused for many years once the original bank of batteries needed replacement. We did several studies of the situation in 2003 - 2004 with an intern from Harvard, checked out the panels, and proved all the system components were still in good shape, but nobody wanted to invest in a new battery bank. So for want of an inexpensive energy storage solution, the entire system, once a beacon of progressive ideas that AUC proudly put on the cover of its brochures, was quietly dismantled and hidden from view. The rumor that went around was "solar isn't feasible". The reality was that the urban electric grid was extended to the DDC building, but grid-intertie was not permitted, and the subsidized electric costs (5 times below market price) forced a move away from decentralized power solutions.
One solution to storing energy at the household or small instittutional level when there is neither feed-in-tariff/grid-intertie capability nor economical battery availability has been to suggest people use the electricity to create hydrogen. This is not so far fetched for Egypt or for the urban poor, particularly as they could theoretically electrolyze contaminated water to get their fuel and partially solve the wastewater problem at the same time. Without even beginning to get into the costs of fuel cell technology there are plenty of ways to modify existing appliances to run directly on combustible hydrogen, as can be seen in this product video by the U.S. startup company "AllH2", whose motto is "think your power comes from the power company? Think again".
But the AllH2 patented residential technology, and others like it, are way beyond the means of the urban poor, and self--built electrolysis apparatus is still expensive and probably difficult to find or even assemble from local materials in Cairo, as would be safe, reliable, cheap tanks for H2 storage (if I am wrong, and somebody would like to show me how to make a cheap electrolyzer and H2 storage system I would be much obliged -- I looked around for Nickel-Plated steel screens in Attaba Square to try and build an apparatus I saw on youtube, but couldn't find anybody who could help me decide if the screens they sell there would work; somebody told me all stainless steel screens have enough nickel in them, but I don't know if I can trust the local merchants in this venture). And I have no idea how to safely compress home generated hydrogen.
Another home energy storage option would be to use the electricity created during the day (solar) and during windy times (windpower) to pump water. In this regard small scale solar and wind make fine solutions for urban households in Cairo, almost all of whom must use electricity and a privately owned pump to get water up to their apartments, since municipal water pressure is insufficient.
The best solution would be to use small wind and solar systems to pump the water from ground level up to a holding tank on the roof. By the end of the day (or the gusty period) the tank is full and the residents can use the water at night.
The notion of recapturing electricity through a micro-hydro turbine (a small Harris turbine or Pelton wheel) is exciting, and even conjures up images of using rooftop rainwater to generate electricity during the yearly storms, but the costs of micro-hydro turbines are much more than investing in a good battery bank, to say nothing of the infrastructure and plumbing costs of such a system. I'm not against the concept, but won't be spending any of our limited funds on such an experiment just yet!
The most exciting solution I've stumbled on to date is one that should have been fairly obvious to me as somebody who has worked with 3 small wind generators (one that we installed in the Meskital slums of Guatemala, one that we put in Cairo and one that we have here in Germany): Use the Windmill to Heat Water!
Naturally one would not use photovoltaics to heat water -- the same surface area can much more efficiently be covered with a solar thermal panel to directly heat the water of a household without all the losses from transforming light to electricity and then into heat through electrical resistence. But with wind power you have a whole different ballgame.
For one thing, many households in the parts of Cairo Solar CITIES works in, particularly homes surrounded by high rise buildings in Darb Al Ahmar and Zabaleen homes under the Muqattam hills, are severely shaded by neighboring structures. In the Zabaleen area we have begun to investigate using city garbage and pig waste to make biogas fuel. But in Darb Al Ahmar this is not an option. Wind power, however, may very well be an option.
For one thing, city landscapes often channel and amplify winds due to the "venturi effect" so there are places in the city that get quite powerful gusts of wind because of the topography of the built environment. Some buildings are tall enough to be very windy on top. And once a year, during the "Khamseen" time in March, the winds blowing off the desert get so strong that they knock pigeon houses off the roofs of buildings. This is energy that could be captured and utilized. But because it is intermittent, it needs to be stored. The beauty of using wind power to heat water is that windmills can be set up relatively far from the apartment that uses them. Personal windmills (like the ones I've seen on the tops of some buildings in Dublin, Ireland) could be located on the Muqattam hilltop itself and the electricity run by wire down to the home beneath, or could be located on the top of a building that sticks up in Darb Al Ahmar, and run to the family unfairly shaded below. The wires would then connect to a resistance heating element in a water heater. Over the course of the day and night the trickle of electricity would gradually heat up the tank for the family. Some days "wind heating" would
supply all the energy needed, others it would merely supplement by pre-heating the water, which would then be heated using conventional means. It could shave quit a large percentage off of the gas or electric bill over time.
The funny thing is that I had neglected this idea even though it is considered standard practice to hook a heating element up to a wind generator! The rationale for hooking an electric heating element to your small wind generator is to protect the windmill from burnout when high winds come and there is an insufficient load on the consumer end. If your battery bank is full and you are asleep and all your appliances are off, the electrons must go somewhere. Most windmills, like the Air403s that I buy, have built in regulators that keep the battery from overcharging, and internal braking mechanisms to try and stall the blades to prevent overload. But overloads can easily happen nonetheless, so manufacturers suggest you have a heating element or some other "dump load" connected. The heating element is recommended to be kept in a small bucket of water, to take away the excess energy.
But because I am sometimes the typical "blinkered" planner, used to putting solutions in neat little boxes, it never occurred to me to think of making that little overload heating element functional!
Today, while investigating using recycled aluminum foil as a fuel source, I stumbled upon the Thermodyne System's intriguing (if disastisfyingly vague) burnaluminum.com website, and one click away I was led to their website claiming it was possible to use home wind generators to create "Hot Water with No Batteries Needed".
The theory seems sound but Thermodyne's website design doesn't inspire confidence. That's okay, I don't blame people who are selling renewable energy products at bargain basement prices for not wasting money on good web design if their concepts are good. There are other sites that talk about the same idea (but suggest using a battery buffer between windmill and water tank for load leveling, though they suggest using an easily obtainable little 4 amp-hr 12v motorcycle battery is sufficient).
As usual in the marginalized "home power" field, we just have to bite the bullet and get out there and test it! It could be that for families with inadequate solar exposure but lots of wind, using windmills to heat water is a great way to think of urban energy storage and distributed generation.