Zero Net Energy 2.0
Big Hairy Audacious Goals. Jim Collins and Jerry Porras described them in their book Built to Last as a success strategy of visionary companies. What exactly is a big hairy audacious goal (BHAG)?
A BHAG is an “audacious 10- to 30-year goal to progress toward an envisioned future… A true BHAG is clear and compelling, serves as unifying focal point of effort, and acts as a clear catalyst for team spirit. It has a clear finish line … people like to shoot for finish lines.”
In 2008, the California Public Utility Commission established a few BHAGs of its own: By 2020, all new residential construction in California will be zero net energy (ZNE). The regulators defined zero net energy as a project that “employs a combination of energy efficiency design features, efficient appliances, clean distributed generation, and advanced energy management systems to result in no net purchases of energy from the grid.” By 2030, all new commercial construction will meet the same goal.
California calls its ZNE goals Big Bold Energy Efficiency Strategies, or BBEES, “not only for their potential impact, but also for their easy comprehension and their ability to galvanize market players.” Indeed, ZNE captures the imagination and inspires action. A goal to achieve zero net energy provides a tangible benchmark with an ostensibly clear finish line—at least on the building or community level.
But what about the system level? Does a world of zero net energy buildings make for a sustainable energy future?
Applying ZNE design principles has the potential to create superior environmentally sustainable buildings with multiple benefits. The design considerations that go into making a ZNE building dramatically more efficient can also simultaneously improve indoor environmental quality, comfort, and occupant satisfaction. For example, buildings that use daylight as a primary source of ambient lighting will generally have better indoor visibility. Attention to airflow in buildings results in better ventilation, and fresher interiors.
Also, by design, most ZNE buildings will interact with the electricity grid. While no one definition standard exists, ZNE is often defined as achieving a net-zero energy balance annually through on-site renewable generation, provided from sources such as solar photovoltaics (PV) or biogas-powered fuel cells. However, while the time scale of ZNE is annual, our electricity system operates on a smaller time scales—starting with milliseconds. Unlike other commodities, electricity cannot be stored cost effectively, which means supply and demand must be matched at all times. No more, no less.
A DG and ZNE customer receives less energy from the utility but still relies on the grid for power supply and network services to export power to the grid.
Although the total amount of energy demanded from the grid is smaller through efficiency and on-site renewable generation, the ZNE’s demand profile changes substantially. On smaller timescales, such as hours, day and weeks, the amount of grid power that must be imported or exported could fluctuate considerably. In fact, a ZNE building’s peak demand on the grid could be when it is exporting power. These phenomena represent a fundamental shift in the formerly one-way power system from both a technical and institutional perspective.
With the proliferation of more ZNE buildings, there could be steeper peaks and valleys that the grid will have to meet. If the building-grid interaction at smaller time-scales is not considered, as might be the case for some ZNE buildings, these buildings could have unintended consequences for the electrical grid and/or miss opportunities for additional value creation.
In Reinventing Fire, RMI looked out to 2050 and asked what it would take for the U.S. economy to dramatically and profitably reduce fossil fuel consumption for the benefit of our nation’s security, health, environment, and pocket books. What is the future vision, and what would the transition entail? In the buildings and electricity sectors, two key themes emerged: efficiency and flexibility.
First, efficiency will remain the least expensive, least risky option for meeting our growing demand for electricity services in the 21st century. Not only is efficiency the most cost-effective option for customers in the short run, it also enables massive cost savings for the system in the long run. The more electricity we save, the smaller the investment in infrastructure we must build to generate and deliver it.
Second, flexibility will become increasingly valuable in an evolving electricity system, which will require new operating and planning mechanisms, rules, and market structures. That need for flexibility will be twofold: 1) strategic flexibility to respond and adapt in a changing environment and 2) physical flexibility in the grid to adapt to major renewable energy sources, like wind and solar, which fluctuate with the weather. On the latter, having sufficient flexibility, in the form of responsive demand, fast-acting power plants, or even storage, will be key.
The Implications—And Opportunity
These principles also apply to how we define and design ZNE buildings and communities. Like investments in the electricity sector, buildings have long lifetimes; decisions made today define our future. Our designs must be flexible in not only how they perform for occupants but also in their interactions with the system at large. A more flexible load shape will have significant value in the emerging future.
To create a truly sustainable energy future, we must coordinate and calibrate our ZNE and grid interactions. Connected to larger ecological and utility systems, ZNE buildings will need to operate as metabolic nodes, exporting electricity to the grid and acting as electrical or thermal storage systems when needed. By itself, ZNE is insufficient to describe the energy performance of a building and its role as an active participant and contributor to the electricity system of which it is a part. To be the most beneficial, ZNE will need to take into account the interaction with the electricity grid. Recent conversations around the world are starting to explore methods for integrating quantitative indicators, which designers could include as they consider design options.
Advances in IT and demand-side technologies that enable bidirectional power flow, distributed intelligence, and operational control will enable the interaction between buildings and the grid to be “richer” in information and interaction. Like biological systems, they will be able to flexibly sense and respond to optimize their interaction with their surrounding environment. As a result, the role that customers and buildings play will expand.
We have the opportunity to design new avenues of communication between utilities and buildings, which are both critical aspects of the same overall system. The ZNE building future is fast approaching us, with broad appeal and manifold implications. Figuring out how the interdependence of these components are optimized may be the biggest opportunity for us to implement our BHAG of a low carbon renewable energy future.