Flexible urban energy in a low-carbon electric world
Keywords: Energy Resources Engineering.

A large and rising share of carbon dioxide emissions is attributable to the electricity sector. The electrification of heat and transportation will have broad consequences for our energy systems and for the electricity sector. Improperly managed, massive electrification could destabilize power grids, cause blackouts and dramatically increase the cost of electricity. Carefully integrated, however, heat and transportation could represent a sorely needed flexibility resource as we turn towards generation sources that rely heavily on the wind and sun. Urban environments are at the core of the transition for our energy systems and are accordingly a central focus of this work. We develop and use advanced computational tools to tackle energy and carbon management problems. To continually monitor decarbonization progress and track emissions in the electricity sector, new tools are needed. Our efforts to provide such tools are described in chapter 2. Since the availability of solar- and wind-based electricity generation varies throughout the day and in space, so does the carbon impact of drawing electricity from the grid. By leveraging publicly available plant-level electricity and emissions data on the hourly operations of the US power system, we traced embodied emissions flows in hourly electricity exchanges between the US electric balancing authorities in 2016. The dataset we built can be used to provide better carbon accounting tools and to estimate the environmental footprint of electricity consumption. To enable the real-time tracking of power system emissions, a second hourly emissions estimation method was subsequently developed that relies on hourly electricity data and technology-specific emissions factors. These hourly electricity data were also used assess the impact of high shares of renewable generation from water, wind and sun on fossil generation sources and on exchanges. As they become even more interdependent with the electric sector, urban energy systems will need to become more integrated and flexible. We will need to pay close attention to the way they operate. This is the focus of chapter 3. Decarbonization of electricity generation together with electrification of energy-and-carbon intensive services such as heating, cooling and transportation is needed to address ambitious climate goals. The Stanford campus district energy system (Stanford Energy Systems Innovations project; SESI) is roughly equivalent to a city of population 30,000 and provides a unique source of real data as well as an ideal testbed for new ideas and control algorithms. We explored whether city-scale electrification of heat with large-scale thermal storage also cost-effectively unlocks operational benefits for the power sector. We built an optimization model of fully electrified district heating and cooling networks integrated with other electric. Using our modeling approach, we computed optimal operational strategies for the controllable loads and thermal storage in this system under different economic hypotheses such as least-cost scheduling and carbon-aware scheduling, that takes advantage of variations in power grid carbon intensity. We also explored the interactions between urban energy systems and large-scale electric vehicle charging. Our modeling efforts on capacity-based demand response led to a megawatt-scale experiment in the summer of 2018, when the campus participated in one of Pacific Gas & Electric's demand response programs. During this experiment, the campus energy operations were significantly modified to provide 5 MW load drops during demand response events. Scientific contributions included approaches to (i) determine how much capacity to nominate each month (the planning problem) and (ii) adjust hourly operations schedules in real time, while preparing for possible events (the control problem)