for those panels is plentiful, deep efficiency may not be necessary in your net zero energy math. You might think you can get away with a pretty mediocre building and make up the difference with cheap solar panels. Not so fast. There’s something called the Duck Curve.
Graham Irwin, of Essential Habitat in Fairfax, California, was among the first in the Passive House community to write about the Duck Curve, a daily dynamic in California energy markets that net zero energy buildings might worsen. Happily, so much solar energy is being deployed in California that demand for nonsolar energy during the sunniest part of the day is approaching—sometimes even reaching—zero. (This dip in demand is the belly of the “duck.”) The problem is that in early evening, just as people arrive home and power up their houses and HVAC systems, the sun goes down and all that solar energy disappears from the grid. This one, two punch of the drop in solar energy and spike in home energy consumption causes demand for nonsolar energy to ramp up extremely rapidly. (This spike in demand is the neck of the “duck.”)
Carbon-intensive peaker plants have to kick in to supply this evening energy demand, negating much of the emissions benefit of net zero energy buildings’ rooftop solar systems. The power of Passive House design is that it turns your building into a virtual thermal battery, maintaining even interior temperatures throughout day and night with almost zero energy input. If more buildings in California were Passive Houses, fewer households would be powering up their HVAC systems in early evening, and that spike in demand for dirty energy would flatten out the neck of the “duck” every day.
As more utilityscale battery storage facilities come on line, and as behind-the-meter home battery storage becomes cheaper, that will further flatten the “duck.” When it comes to rooftop solar and Passive House, it’s not either/or, it’s both.
THE SEASONAL LENS
Exciting as batteries are for both grid and home energy storage on a daily basis, they are ill equipped to deal with the seasonal intermittency of solar energy. One of the trickier clean-energy puzzles that humanity will need to tackle is how to power northern climates during the winter. Part of the solution will be more widely interconnected energy grids, so that southern sun can provide northern supply. Part of the solution will be wind and hydro. Another part of the solution will be power-to-gas, where excess solar energy produced wherever and whenever it is most plentiful is used to split water into hydrogen and oxygen, and that hydrogen is stored as fuel. But another key part of the solution lies in our buildings, because the thermal battery of deeply energy-efficient buildings is perfectly suited for seasonal storage. By dramatically reducing winter heating load, Passive House buildings could play a starring role in solving the northern winter load conundrum.
When it comes to a clean winter grid and Passive House, it’s not either/or, it’s both.
EFFICIENCY IS THE ULTIMATE DISTRIBUTED-ENERGY RESOURCE
The core reason that deep energy efficiency is likely to remain centrally important both to the clean-energy transition and to global climate action is that it is the ultimate distributed-energy resource. Not only can energy efficiency be deployed virtually anywhere, but that efficiency performs best exactly when it is most needed—during peak demand. Energy efficiency flattens out the peaks and valleys of demand, both on a daily and on a seasonal basis, making it more practical to fill in the gaps with renewable energy, battery storage, and demand response.
Not only is Passive House still relevant in these early days of the clean-energy revolution, but it will support the revolution’s future success.