Using Integrated, Intermediate-Scale Infrastructure To Improve The Grid
The past 75 years of U.S. infrastructure development has pushed toward large, centralized utilities through policy treating electricity, sewage, and water as public goods. Economics ignorant of externalities drove the sources of energy services (electricity, heating, and cooling) to cheap, readily-available fossil fuels. The result is infrastructure that loses 6% of electricity, 2.5% of natural gas, and uses only 40% of the energy present in the fuel source.
In response, distributed electricity generation is growing. The Solar Energy Industry Association reported that 2014 was the first year residential distributed solar eclipsed utility-scale installations; Pike Research expects this market to reach $154 billion annually by 2015. Yet the California Independent Systems Operator (CAISO) warns that high levels of distributed solar could lead to imbalances and shedding low-carbon generation in hours when production outpaces consumption. Even if this worst-case scenario does not manifest, the time-of-use disparity in electricity production and consumption requires a solution. This is where an intermediate-scale, integrated planning has significant promise.
The most talked-about solution to this problem is on-grid storage. Tesla, Aquion, and others are innovating toward lower-cost and lower-loss batteries. Yet even this is a patch for a systemic problem—how to design the grid so that supply and demand are balanced. Demand-side management helps address this issue, but there is an even more nascent design intervention that consistently is unutilized: smart planning of buildings, loads, and municipal water and waste infrastructure to fully utilize resources by design.
Solving this problem starts by treating buildings as part of the grid. Traditional planning assumes that zoning and building technology are separate from electricity infrastructure planning, and that both are divorced from water, waste, natural gas, and sewage infrastructure. Even recognition of the interdependencies of these systems at a macro-scale has not driven local utilities, regulators, and planners to see them as interconnected. Yet to fully utilize resources, address the temporal mismatch of electricity generation and consumption, and improve grid performance, we need to see these systems as interconnected.
The irony is that this means reverting to a planning style from the earliest days of electricity. New York, San Francisco, Chicago, and other cities were built using cogeneration of heat and electricity from fossil fuel combustion. Sale of steam (for heat) and electricity was required for utilities to be profitable. In the 1930s, however, cheaper fossil fuels and federal incentives drove generation from the cities, forcing a shift to stand-alone electricity generation that required new gas infrastructure to heat buildings, and meant combusted resources could no longer be utilized as efficiently. 75 years later, when concerns over carbon rule the environmental narrative, reverting to combined services at an intermediate scale that maximize fuel efficiency can improve urban sustainability. This requires a planning ideology that groups at Stanford, universities in China, and several companies are now pioneering. It involves breaking down the silos of traditional infrastructure planning and finding ways to fully utilize heat, electricity, graywater, solid waste, and wastewater when they are available and when necessary, storing them in forms that provide flexibility for an integrated infrastructure network. It also involves realizing that some synergies are only available at intermediate scales where the domains of water, energy, and waste overlap.
The canonical example mentioned earlier is cogeneration, or its descendant, trigeneration. Cogeneration involves burning a fuel (traditionally fossil fuels, but potentially biomass or hydrogen) to produce electricity and then capturing the waste heat for use in industrial systems or space heating for buildings; this is currently done at the Cardinal Cogen facility on the Stanford campus. Trigeneration builds on this by using the heat in an absorption-cycle refrigeration process to produce chilled water for space cooling. While the electricity grid and distributed heat provision through natural gas have a “well-to-wheel” efficiency of about 40%, cogeneration and trigeneration can achieve upwards of 60% efficiency. Furthermore, they reduce the midsummer peak on the electricity grid by serving cooling load with heat rather than electricity. These efficiencies can be driven higher if we include zoning in infrastructure planning to balance end-use loads. Commercial and residential buildings, for instance, use heat, cooling, and electricity at different times. Smart zoning policy can distribute these in a manner that balances consumption from local power systems, alleviating grid stress and improving efficiency.
Stanford’s Cardinal Cogen Facility (Photo: Stanford News Service).
While trigeneration is often a hard sell in the U.S., developing nations like China have an opportunity to utilize district energy networks to solve mounting environmental and development concerns. China builds the square footage equivalent of Chicago annually, and will for 20 years. Its electricity grid is less efficient and more polluting than the U.S., emphasizing the need for smarter resource use. In these conditions, ongoing research at Stanford has shown that informed planning of building types with trigeneration can reduce emissions from municipal infrastructure 25-50%.
The same impacts may not be easily achieved domestically. The high cost of retrofitting cities with hot and chilled water networks is likely to be prohibitive for many municipalities. But the same principal of locally capturing the full benefit of resources applies. Distributed wastewater and graywater treatment technologies can serve as buffers to utilize excess renewable electricity at the time it is produced. Anaerobic digesters and reverse osmosis can even profit from colocation with a thermal power plant by utilizing the heat to accelerate treatment. Distributed heat sources solar panels and data centers can be utilized for distributed water treatment or space heating. Even heat pumps and geothermal cooling systems can leverage small networks of buildings to improve efficiency by balancing loads and avoiding inefficient operating conditions.
Yet all of this requires a change in infrastructure planning from silos to an integration that considers services rather than goods, and is parallel rather than sequential. The tools and methods for this paradigm are still being developed, but the cultural shift needed to embrace parallel, distributed planning must start now if we are to leverage integrated infrastructure to improve urban sustainability.
Cover image "A cogeneration thermal power plant in Ferrera Erbognone (PV), Italy" by Mattia Luigi Nappi - Own work, CC BY-SA 3.0.