Smart Net Zero (Part 1)

Net zero energy or net zero carbon have been established as prime goals for sustainable, high-performance buildings in the Architecture 2030 Commitment, the Living Building Challenge, LEED Zero and other frameworks. This makes sense as a way to encourage greater efficiency and more renewable energy distributed generation, working toward decarbonization. It is a simple metric that can be applied to individual buildings where the owner has control over the energy within the boundaries of their property. However, as the quantity of distributed generation increases within the current system of regional utility production and distribution, net zero energy can have a perverse effect. California, a state with a large and growing proportion of grid-connected renewable energy, offers a good illustration.

Over a typical year, California generates approximately 70% of its own electricity and imports the rest from neighboring states. In summer, especially in the late afternoon when air conditioning demand is highest, solar production tails off and domestic use ramps up, California relies heavily on imported power. In the spring and fall, the combination of utility-scale and rooftop solar peaks midday and exceeds the load, so California typically sells energy to its neighbors. Sometimes neighboring states don’t want this energy, and the wholesale price of electricity goes negative.

Solar and wind farms, which can instantaneously cease production, do exactly that (this is called economic curtailment), giving unharvested electrons nothing do to except meaninglessly heat up the solar panels. However, most fossil fuel generators (and all nuclear generators in the U.S.) lack this flexibility and find it economically preferable to sell their energy at a loss for a few hours so they can be ready to profit a few hours later (see graphs (left) of energy consumption and wholesale price fluctuations on typical spring and summer days). Throwing away fully paid-for solar and wind energy raises the cost of decarbonizing our grid.

As more distributed solar generation is added to the existing “not-so-smart” grid to meet new code requirements and growing consumer demand, this unfortunately results in the more frequent economic curtailment of existing utility-scale renewable generation and a disincentive to develop more.

Given that a gigawatt-scale solar farm has approximately one-third the installed cost per watt of a residential rooftop array, perhaps we need think beyond simple net zero building requirements to take a smarter systems approach. One way to address this is with smarter buildings and smarter consumption. While the cost of batteries continues to drop, and they are undoubtedly part of the long-term solution, there are still economic, environmental and practical barriers to widespread adoption and deployment of battery storage. Instead of storing excess solar energy, a lower cost solution is to simply use that energy by employing smart controls on key systems to strategically adjust when our buildings use energy.

For example, rather than a thermostat kicking on the air conditioner right before you return home from work, it could instead be programmed to supercool your home in the middle of the day when solar panels are producing free energy that is going unused, allowing the home to coast into the evening with comfortable indoor temperatures and limited energy use as solar production tapers off. Since wholesale prices of electricity are generally known a day in advance, smart buildings can optimally schedule consumption to maintain comfort, reduce costs, and reduce the need to curtail solar and wind production. Of course, smart consumption will require smart pricing.

Not only will that smart day-ahead pricing encourage the use of solar and wind energy when they are abundant, it will also allow consumers to avoid using electricity when it is expensive, reducing energy bills. This is especially true during hot summer afternoon peaks when using electricity often requires the grid to use expensive fossil fuel-based power.

Smart consumption also helps in emergency situations, like when windy, hot, dry conditions increase wildfire risks and cause the utility to de-energize high-risk powerlines. Areas exclusively served by those lines will lose all power. However, most areas served by high-risk lines are also partially served by other lines that are incapable of delivering 100% of the needed power. In a not-so-smart grid, those areas also must be de-energized. However, rather than imposing blackouts on these partially served areas, a utility could signal the impending emergency, with customers automatically limiting their energy use to necessary uses like lighting and communications equipment, while others might scale back certain uses but preserve power to critical equipment (medical, security, etc.). Not a perfect solution, but much better than what we have seen recently in California. The same is also true for large natural disasters like earthquakes, when the grid might be able to supply some, but not all the normal demand. Smart consumption can allow at least the most critical needs to be met.

We should certainly continue to advocate for net zero energy, but in a smart way, not solely focused on each building as an energy island. Next month, we will look at other smart approaches to net zero and the cybersecurity challenges that a smarter energy future creates.

Alan Scott, FAIA, LEED Fellow, LEED AP BD+C, O+M, WELL AP, CEM, is an architect with over 30 years of experience in sustainable building design. He is a Senior Consultant with Intertek Building Science Solutions in Portland, Ore. Dan Bihn is energy educator, communicator and consultant specializing in smart energy issues. To learn more, visit www.intertek.com/building/building-sciences/ and follow Scott on Twitter @alanscott_faia. Bihn can be reached at dan@danbihn.com.