Net-Zero Buildings

Urban energy networks are at risk from climate change. Heat waves increase grid demand as people compensate by air conditioning their homes and offices, rising sea levels threaten offshore energy supplies, and severe weather and storm surges have the potential to incapacitate the grid for days, if not weeks, because of the damage they cause to power lines and plants. There are several ways to make energy networks more resilient on a local scale (across MIT’s campus).

Reducing grid demand should be a primary goal of improving climate resilience, because this makes buildings and communities less dependent on large, centralized electricity networks that are more vulnerable to severe weather damage. One way to accomplish this is by decentralizing energy, by distributing it through smaller, single-unit renewable energy systems like rooftop solar and wind turbines. These are easier to repair and less vulnerable in the event of catastrophic grid damage. Reducing grid demand also means events like heat waves will not cause demand to exceed output, thereby making communities more resilient to heat.[1]

An innovative strategy in minimizing grid demand is the trend in net-zero buildings: buildings that have a zero or negative net use of energy from the grid. There are many ways to achieve net-zero buildings, though some are more practical than others given the climate of Cambridge. This will require a combination of energy-saving and energy-generating efforts. Energy-saving efforts might include collecting and repurposing rainwater, installing a green roof for natural cooling, using sunlight for natural heating, using computer systems to regulate and minimize energy usage, and using innovative insulation materials.[2] Likewise, energy-generating efforts might include installing transparent solar cells in windows,[4] generating power from rainwater flow off the roof,[5] and using single-unit rooftop wind turbines like those currently in use on the roof of Boston’s Prudential Center.[6]

Source: A New Way to Store Solar Heat.[3]

In regards to the increasing frequency of extreme heat waves, the cooling systems in net-zero buildings are often much more efficient than current, electricity-dependent cooling systems that may become unreliable when they are most needed. Green roofs, for example, absorb heat and act as building insulators. Estimated costs start around $10/foot, but despite the considerable upfront cost, the energy savings pay off quickly. A University of Michigan study estimates that green roofs save on average $200,000 over their lifetimes in comparison to conventional roofs, and most of these savings are from the reduced energy needed to cool the building.[7] Taking into consideration New England’s large seasonal variations, protruding “awnings” over windows that account for seasonal sun angle, letting in maximum sunlight in the winter and shading windows in the summer. Likewise, positioning openable windows to account for dominant wind direction can help maximize natural cooling in warmer months.[8]

There is great potential for these strategies to be pilot-tested on MIT’s campus, especially in new buildings. The new dormitory on Vassar Street, set to open in Fall of 2020, would be a perfect place to experiment with net-zero technologies, for example. Similarly, newer buildings like Simmons Hall or the Stata Center could be testing grounds for these technologies, because since they are newer, they lack many of the ventilation and insulation issues that tend to exist in older buildings.

By Julia Wyatt

 

References

  1. Power Failure: How Climate Change Puts Our Electricity at Risk. (2014, April). Retrieved from http://www.ucsusa.org/global_warming/science_and_impacts/impacts/effects-of-climate-change-risks-on-our-electricity-system.html#.Wg8tYhNSzR0
  2. Drawdown. (2017, February 7). Net Zero Buildings. Retrieved from http://www.drawdown.org/solutions/buildings-and-cities/net-zero-buildings
  3. http://frasiers.com/wp-content/uploads/2015/02/Net-zero-home-637-px.jpg
  4. Chandler, D. L. (2016, January 7). A new way to store solar heat. Retrieved from http://news.mit.edu/2016/store-solar-heat-0107
  5. Coxworth, B. (2014, March 26). Rainwater used to generate electricity. Retrieved from https://newatlas.com/pluvia-rainwater-microturbine/31379/
  6. Mitanis, M. (2016, March 8). Prudential Center’s Long Awaited Final Phase Nears Completion. Retrieved from http://skyrisecities.com/news/2016/03/prudential-centers-long-awaited-final-phase-nears-completion
  7. Environmental Protection Agency. (2014, June 17). Using Green Roofs to Reduce Heat Islands. Retrieved from https://www.epa.gov/heat-islands/using-green-roofs-reduce-heat-islands
  8. Autodesk. (n.d.). Net Zero Energy Buildings: Passive Heating, Cooling, and Ventilation. Retrieved from https://sustainabilityworkshop.autodesk.com/sites/default/files/core-chapter-files/autodesk-sustworkshp_netzeroenergybuildings-passiveheatingcoolingandventilation.pdf