When thinking about Zero Net Energy Commercial Buildings, the most important thing is how you get to net. Many have willfully (it seems to me) accepted the delusion that carbon credits will be a useful or perhaps even significant component of this net. Such people suffer from a failure of imagination. They do not imagine that there will be new technologies.
They have also fallen into the fallacy that tomorrow will be a straight line from today. Today you can buy carbon credits fairly easily. My favorite source is free carbon offsets. These will not be so easy to come by in time. For one thing, the FTC is already looking into their fraudulent issue, sure to reduce the supply. The more important reason is that if we move in any significant way toward the 2030 challenge (or should I call that, after EPACT 2007, the 2025 mandate?) there will be many, many more buyers. More buyers chasing less product will be, as always, a prescription for rapidly rising prices.
The more important net is the honest balance of consumption, generation, storage, and purchase. Most sites will need all four.
Consumption gets most of the attention today. Reducing consumption gets the press. We know how to reduce consumption. It will not get us to zero, though.
Generation is pretty well understood as well. We will need to keep a close eye on real life metrics to make sure we are not swapping relatively clean distant generators for dirty (and noisy) generation locally. This demand will provide a ready market for renewable of all types as soon as we learn to smooth demand. And that will require storage.
Storage is the wild card. Storage will need to be a mix of technologies, and even energy types. I have written of storage before (And the winner is…) and of how future markets will create more ways for people to store energy. Some of these, especially some forms of thermal, change the order, i.e., store first, generate (or transform to a more useful form) second. The inefficiencies may even drive the more rapid adoption of the DC Commercial Building.
Nanoptek has recently demonstrated its new store-first, generate later technology, a process that greatly enhances the generation of hydrogen in sunlight by doping nanostructures with titanium. Technology such as this will make it easier to store energy now, and generate later.
We should probably add a fifth item to the energy toolbox of each Zero Net Energy Building – load shaping. Peak shaping can only reduce amenity and performance, albeit in return for price concessions. Load shaping, in which the energy use is not curtailed, but shifted to a different time of day can greatly improve the operation of the power grid. Load shaping is an approach that is more amenable to profound shifts in energy consumption patterns. Load shaping is what makes the other strategies work.
If you own a commercial building, you may be load shaping already. Even without formal storage systems, you may be over air-conditioning in the early morning to save air conditioning during business hours. There are power companies out there that will not only give you discounts, but will pay you for load shifting. And if you build the infrastructure to account for load shaping, you will have the infrastructure you need to manage generation and storage.
Pity, you will probably not be able to get a carbon credit for it. I wonder of the ISO's might award them....