Last November marked the opening of High Point Center (rendering above), a new community center building in West Seattle's High Point neighborhood. On the Center's roof is what is touted to be Washington State's largest installation of photovoltaic solar panels on any single building. Photovoltaic (PV) systems convert incident sunlight to standard household AC electrical power.
Last week the Seattle City Council announced a goal of carbon neutrality for the entire city by 2030. Achieving true carbon neutrality will require weaning ourselves from fossil fuels, and aside from efficiency, the most important strategy for making that happen is conversion from fossil-fuels to carbon-free electricity. What is the potential contribution of PV systems like the one at High Point Center?
Short answer: The fossil fuel-based energy that we currently consume massively dwarfs the amount of energy we could ever realistically expect to generate from PVs.
Longer answer to follow.
The 90 kW PV system at High Point Center will produce about 90,000 kWh of electricity per year. How much energy is that?
According to Seattle's recently published greenhouse gas inventory, in 2008 the average Seattle household's total energy consumption was 21,000 kWh. So the High Point Center PVs could meet the net annual energy needs of four average Seattle households.
Next question: How much PV would it take to generate an amount of energy equivalent to all the fossil fuels currently used by Seattle?
Using PV to match the 10,053,000 MWh of fossil fuel-based energy consumed by the City's residential, commercial, and industrial sectors in 2008 would require 112,000 PV systems like the one at High Point Center, and the panels would cover 36 square miles. Not trivial, to say the least.
The transportation sector is less straightforward. For this analysis I'll stick to road travel, which is 40 percent of the City's total carbon footprint.
Previously, I estimated that 1,100,000 MWh of electrical energy per year would be required to power Seattle's entire fleet of cars and light trucks if they were all electric. Assuming electric commercial trucks would be on average one fourth as efficient as electric cars, that comes out to roughly 2,000,000 MWh annually for all road travel in Seattle—equivalent to 23,000 High Point PV systems covering more than seven square miles.
So, to offset fossil fuel consumption for Seattle's whole enchilada—residential, commercial, industrial, and road transportation—we're talking 43 square miles of PV. Not exactly practical, given that Seattle's total land area is 84 square miles.
And then there's the price tag of such a colossal amount of PV. At current installed costs of $7.60 per watt, the project would set the City back $90 billion. Ahem.
(Anybody still with me? Anyone checking my math? OK, take a deep breath.)
The take home point here is not that PVs are a waste of time—they aren't. The value of this thought experiment is that it puts some perspective on the big picture limits of one alternative. Because we use such a huge amount of fossil fuel-based energy, there is no silver bullet solution—and in reality, there is no viable one-for-one energy replacement for fossil fuels, period.
Compared to most other cities, the prospects for carbon neutrality in Seattle are better because our electricity is nearly carbon free. But even with all the new carbon free energy sources we can realistically bring on line by 2030, achieving true carbon neutrality is still going to require a major reduction in the amount of energy Seattleites consume—on the order of a two-thirds reduction is my best guess.
What would that society look like? In 1950, per capita energy use in the U.S. was one third lower than it is today, but that wasn't because their energy infrastructure was more efficient—the opposite was true. People used less energy in 1950 because they lived in smaller houses, traveled less, and had fewer appliances and electronic gadgets.
If we aggressively pursue efficiency—and that includes location efficient land use patterns that enable reduced single-occupant vehicle travel—in concert with the full spectrum of carbon-free energy strategies, then carbon neutrality need not require any sacrifice in quality of life. And in fact, there is much to be gained, such as energy independence, the creation of green jobs, and the reduction of car dependence.
Indeed, if we hope to inspire people to rise the challenge of achieving carbon neutrality, we must reframe the discussion such that climate change is perceived not as a crisis, but as an opportunity.