By: Matthew Fickett, AIA, CPHC, LEED
What does “Net Zero” mean?
In this discussion, what I mean by “Net Zero” is that the world would be just the same if the building didn’t exist. Without the building, the sun shines on the earth, and the sunlight is transformed into heat. This tells us that our only allowable input is sunlight, and the only thing we can emit is heat.
Right away, you can see that fossil fuels break the rules. There’s an input (oil or gas) and an output (smoke into the atmosphere). That process definitely doesn’t leave the world the same as it would be if the building didn’t exist.
So, what energy source can we use?
At first glance, it seems like if we have to depend on sunlight, the only allowed energy source for the building is photovoltaic panels (solar panels). Actually, many other energy sources are just a complicated way of taking sunlight, using it, and turning it into heat. Wind turbines capture energy from air which moves because sunlight caused wind. Dams capture energy from water which was deposited upland after it was evaporated by sunlight. There are many other examples, but in general, any renewable source of energy meets our criteria: it captures the sun’s energy for us to use, and then the only output is heat.
Also, you’ll notice that there’s no rule that the energy source has to be close to the building. To create a building which is net zero, we don’t need to use only on-site renewables (like solar panels on the roof); we can use solar panels across the street, or in another state, or wind farms offshore. The only thing we can’t use to achieve net zero is an energy source which turns fossil fuels into smoke in the atmosphere.
All these sources have one thing in common: they are all electric. Therefore, our building must run entirely on electricity.
What does this mean for the building?
The main use of energy in buildings is space conditioning – heating and cooling. In conventional construction, cooling is already all-electric, but heating is usually not. It is very common to have a gas-fired heating system in a building. Fortunately there is a common solution already available in the form of heat pumps.
A heat pump is a machine which uses electricity to move heat from one place to another. This in contrast to electric resistance heat, which turns electricity directly into heat. That’s wasteful: for every unit of electricity, you get exactly one unit of heat. With a heat pump, instead, you use one unit of electricity to move three or four units of heat. You probably already own several heat pumps in your home: a refrigerator is one (moving heat out of the fridge into your kitchen); a window air conditioner is another (moving heat out of your room into the outdoors).
There are two pieces of good news: first, heat pumps can run in either direction. The same heat pump can cool the building in summer, and heat it in winter. (With some clever engineering, it can even do both at once.) Second, heat pumps get more efficient the bigger they are. A house-sized heat pump might move three or four units of heat per unit of electricity. A heat pump suitable for a very large building or a small campus might move more on the order of six or seven. Some utility-scale heat pumps in Europe report a Coefficient of Performance (COP) approaching nine.
What about labs?
Now that we have the basic pieces defined, the next step is to see how these apply to a laboratory building. For that, please read Part 2 of this series, coming soon.