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Urbanism in the Age of Climate Change: Green Technology


Editor’s note: This week, we continue our 5-part series of excerpts from Peter Calthorpe’s book, “Urbanism in the Age of Climate Change.” This is installment number four. Thanks to Island Press, a few lucky Streetsblog readers will be selected to receive a free copy of the book. To enter the contest, fill out this form.

I was part of the passive solar architectural movement in the 1970s. Its core idea was to provide energy for buildings in the most direct, elegant way. We had disdain for complicated “active solar” systems, with their complex engineering, maintenance, and costs. The passive way was first to reduce the demands by building tight, well insulated structures, flooded with natural light, and then to let the sun’s radiation or the cool night air work with the buildings’ form to provide thermal comfort. The same approach needs to be taken in relation to the climate change challenge: we need to find the simple, elegant solutions that are based on conservation before we introduce complex technology, even if it is green.

We need to focus, ironically, on ends, not means. For example, in passive solar buildings, focusing on the end goal (thermal comfort) rather than the means (heating air) changed the design approach dramatically. It turns out that human comfort has more to do with surrounding surface temperatures than with air temperature in a building, so massive walls that absorb and store the sun’s gentle heat also provide a more comfortable environment without all the hot air. Or, if lighting is the goal, electricity and bulbs are just one potential means; a building that welcomes daylight is the simple, elegant solution—even better than a complex system of wind farms generating green electrons for efficient fixtures. Likewise, the goal of transportation is access, not movement or mobility per se; movement is a means, not the end. So, bringing destinations closer together is a simpler, more elegant solution than assembling a new fleet of electric cars and the acres of solar collectors needed to power them. Call it “passive urbanism.”

Once demands are reduced by passive urbanism, the next step is to add technology. Green urbanism is what you get when you combine the best of traditional urbanism with renewable energy sources, advanced conservation techniques, new green technologies, and integrated services and utilities. All the inherent benefits of urbanism can be amplified by a new generation of ecological design, smart grids, climate-responsive buildings, low-carbon or electric cars, and next generation transit systems.

These technologies function in differing ways at differing scales. There are three scales of such green technology: building, community, and utility. Building-scale technologies are ecumenical; they can be applied in any form of development, traditional urban or auto-oriented sprawl. Obviously, better building insulation, weatherization, and efficient appliances can be used in single-family subdivisions as well as in urban townhomes. So, too, can solar domestic hot water systems or photovoltaic cells. Efficient lightbulbs make sense in any location, as do efficient appliances. While bigger, less efficient buildings will cost more to green, such retrofits and new building standards are the starting point for any sustainable future—but not the final solution.

At the other end of the spectrum are the centralized utility-scale systems. Shifting to massive renewable sources in remote locations will carry the burden of building equally massive distribution facilities. Such a “smart grid,” while essential to moving large quantities of power to our cities from distant natural resource areas (wind, sun, geothermal), has a high capital cost and reduces efficiency because of transmission line losses. These expenses are in addition to costs that are already consistently higher than those of conservation. Also, large-scale solar and wind operations can create big environmental footprints, as large tracts of virgin land are developed.

What are the real needs for large utility-scale renewable energy sources? It depends on the type of communities we plan and how we build them. If we add the travel demand of an average single-family home in the United States to the energy needed to heat, cool, and power the home, the total is just under 400 million Btu (British thermal units) per year (this includes the source energy typically left out of these calculations: the embodied energy of cars, the energy to produce the gasoline, and the wasted energy to produce the home’s electricity). Assume for argument that weatherization and greening this home can reduce building energy consumption by 30 percent and that the family buys new cars with 50 percent better mileage. The result is a 32 percent overall energy reduction—not bad for “green sprawl.” In contrast, a typical townhome located in a walkable neighborhood (not necessarily downtown but near transit) without any solar panels or hybrid cars consumes 38 percent less energy than such a suburban single-family home. Traditional urbanism, even without green technology, is better than green sprawl.

Now add more building conservation measures, green technology, and better transit systems to the townhouse, and you get close to the results we will need in 2050. If you move to a green townhome in a transit village, you will be consuming 58 percent less energy than on a large lot in the suburbs. If you move to a green condo in the city, you will be saving 73 percent when compared to the average single-family home in a distant suburb.

The implications of this for our power grid are massive. If more families lived this way—say just a quarter moved from single-family lots to green townhomes—the generating capacity required for buildings in the nation would be reduced by over 25,000 megawatts per year, eliminating the need for 50 new 500-megawatt plants.22 At $1.3 million per megawatt of installed capacity, that is more than $32 billion of avoided capital cost for new power plants per year.23 The reduced fuel costs and environmental impacts are additional benefits.

The same is true for auto use. For example, satisfying California’s need for more driving in a “Trend” future would result in around 183 billion additional auto miles per year in 2050 when compared to the more urban alternative. Some believe that if we shifted to electric cars running on green electrons, the carbon problem could be solved. However, producing that many green electrons has a hidden hurdle: it would take 50,000 acres of high-efficiency solar thermal plants, 130,000 acres of photovoltaic panels, or 860,000 acres of wind farms (nearly thirty times the land area of San Francisco) to power such a transportation system.24 This would present a giant environmental footprint no matter where it was placed. Ironically, the biggest barrier to such a green, if not urban, solution may be environmentalists themselves, protesting lost desert landscapes or resisting impacts on bird populations by wind turbines (or
even objecting to seeing the turbines on the horizon).

At the middle of the three scales, urbanism offers a better framework for more distributed community-scale energy systems. In fact, there are important community scale systems that can function only within an urban framework. One of the most significant of these technologies is the decentralized cogeneration electric power plant (called combined heat and power, or CHP). Such small-scale power plants can be coupled with district heating and cooling systems to capture and use the generator’s waste heat in local buildings and industry. Currently, for every watt of energy delivered to a home, two thirds is lost as waste heat up the smokestack and in transmission lines.25 Local cogeneration plants coupled with district heating and cooling systems can largely eliminate these inefficiencies. The waste heat is captured and reused, while the transmission losses are greatly reduced. Because of this, it is estimated that cogeneration systems operate at around 90 percent efficiencies whereas standard power plants average only 40 percent.

Married to urban environments, cogeneration offers a cheap, time-tested alternative—one that has been employed by college campuses and European new towns for decades. There, small power plants are placed close to dense neighborhoods and commercial centers, distributing waste heat underground to each building for hot water, cooling, and heating. These plants can burn almost any form of renewable biomass, eliminating the energy-intensive process of converting valuable crops into biofuels or finding mechanisms to transform grass to gas. More interesting are a new generation of “waste to energy” technologies that not only produce green electricity and heat but also avoid the massive landfills and trucking costs of typical garbage systems.

Typically, cogeneration systems are found in commercial applications where waste heat is used in an industrial process and the power generation balances with the electrical demand. It is estimated that in the industrial sector alone, “the potential for CHP generation is equivalent to the output of 40 percent of the coal fired generating plants in the US.” 26 Utilizing similar systems in urban districts would add dramatically to this potential.

Sacramento built such a system in its downtown in the 1970s that burned “gasified” dead wood created by a Sierra Mountain beetle infestation—a net zero carbon system because it used only biomass. In addition, it had twice the efficiency of a remote plant because its waste heat was used to run heaters and chillers for all the state office buildings in the district. But to be effective, such systems are dependent on urban densities and a balanced mix of uses. Sprawl is not a candidate for district heating and cooling systems, as the costs of moving the waste heat to scattered buildings are too high. However, mixed-use urban neighborhoods could top off their energy needs with cogeneration in ways that greatly reduce costs and environmental impacts—easily creating zero net energy communities.

Water and waste systems also benefit from a community-scale approach. Sewer systems can take effluent and biologically recycle it into potable or irrigation water, usable biomass, and methane for cooking. Water demands can be offset by such graywater recycling systems, drought-tolerant landscaping, and indigenous plantings. Stormwater detention and treatment can be decentralized to community-scaled parks and integrated as landscape features. Rather than channelizing streams and rivers, setbacks can allow habitat to coexist with flood protection and trails. As with energy systems, community-scaled water and waste systems can be ecologically integrated in ways that save costs, save carbon, and enhance livability.

From Urbanism in the Age of Climate Change, Chapter 1, by Peter Calthorpe. Copyright @ 2011 Peter Calthorpe. Reproduced by permission of Island Press, Washington, D.C.


22. Assuming advanced natural gas combined cycle plant technology.
23. National Energy Technology Laboratory, “Cost and Performance Baselines for Fossil Energy Plants” (Washington, DC: U.S. Department of Energy, 2007).
24. Calculations based on average capacity factors for each technology, and land use requirements based on case studies of representative electricity-generation facilities.
25. Energy Information Administration, “Annual Energy Review 2008” (Washington, DC: U.S. Department of Energy, 2009).
26. Al Gore, Our Choice: A Plan to Solve the Climate Crisis (Emmaus, PA: Rodale Books, 2009), 254.

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