Energy Efficient Cities: Building-Level Solutions, Microgrids and IoT

In 2017, the U.S. Energy Information Administration (EIA) reported that 39 percent of total U.S. energy consumption was attributed to the residential and commercial building sector, equivalent to 38 quadrillion BTUs. In Europe, this number is 38.1 percent (according to EuroStat). As one of the largest individual consumers of energy, buildings have significant potential for the application of energy efficient technologies.

Small, passive measures such as painting a building’s roof white, shading from the sun or replacing office equipment and electrical appliances can have a massive effect. A recent project in Durban, South Africa, implemented the aforementioned measures in two government buildings and saw energy savings of 15 percent (amounting to 400,000 kWh and a 340-ton reduction of CO2 emissions) and an investment payback period of five months. These simple retrofits have incredible potential with minimal economic ramifications.

Recent studies have shown that building cooling and heating energy demand will go up by anywhere from 7 percent—40 percent. The lower end of this growth assumes that all population growth occurs in urban areas, whereas the larger number corresponds to increases in demand if population growth is strictly suburban or rural (and therefore predominantly housed in single-family homes). Urban areas benefit from the existence of passive factors such as smaller FAC (floor area per capita) which result in more efficient heating and cooling as well as lower heat loss due to a smaller surface to volume ratio.

Active technologies, such as district heating, which would centralize heat generation across multiple buildings could also layer on further efficiencies. Urban living, however, isn’t without its energy tradeoffs—decreased access to solar power, natural ventilation and obstruction by other buildings make many passive design techniques difficult to implement, but a diverse urban fabric would ameliorate the prevalence of those problems and provide more building level access to energy-efficient technologies.

The growth in energy demand will be dominated by new building stock in developing countries and retrofits in established countries. Developing countries should focus on passive approaches such as densification tactics to maximize the scalable energy benefits of urban living, whereas developed nations should turn towards active technology development for retrofits.

In North America and Europe, over 50 percent of all actively used buildings will be retrofitted or replaced in the period from 2010-2050. While retrofitting is a great option, current technologies can already lead to a 20-40 percent reduction in energy use, but deep retrofit technologies that are still under development might lead to a 90 percent reduction in energy use. This creates a premature lockdown of investment, potentially disincentivizing investment in retrofits. Both building owners trying to increase their bottom line and lawmakers enacting subsidies should pay close attention to building life-cycle analyses to determine when current action outweighs potential future technological gain and incentivizes the transformation of current building stock towards higher energy efficiency.

While investment in individual buildings can add up to significant energy efficiency gains within an urban area, a focus on infrastructure allows for more direct global impact and sets the tone for private building owners to innovate in order to take advantage of a more flexible energy system. Two active infrastructural technologies are microgrids and the Internet of Things (IoT).

Microgrids are “a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that act as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island-mode” (CT Public Act 12-148). This means that by leveraging microgrids energy can be provided at a local level by decentralizing electricity production which in turn minimizes the amount of energy loss in transmission. Historically, our grid has been powered by central power stations that distribute energy by means of transmission cables. These grids lose an average of 66 percent of electricity during generation and transmission, whereas microgrids allow for more distributed generation and only lose 33 percent. This means that less fuel needs to be burned in order to meet energy demand.

In traditional grids, 6 percent of the electricity is lost in transmission. By distributing production and placing it closer to consumption, microgrids may substantially decrease this loss. The extra 7-30 percent of energy that's lost in the conversion from AC to DC and back (which is done to either match appliance power standards or to more efficiently transmit electricity through certain environments) can also be minimized since small renewable energy systems provide a larger variety of DC sources and the proximity of production to consumption reduces the transmission need of conversion.

Additionally, due to the size constraints inside urban areas, large power plants that burn fossil fuels are harder to fit into a distributed microgrid so there's a greater economic (and ecological) incentive for the connection of small renewable power generators such as wind and solar which are getting cheaper and more efficient every year. Since microgrids are connected to multiple electricity generators with different energy sources, they are unlikely to experience total failure, which increases the resiliency of our energy networks. This redundancy also allows for smart load matching instead of having to rely on the exorbitant start-up costs associated with traditional fossil-fuel based power plants.

The Internet of Things is a distributed series of sensors that are interconnected, allowing machines to talk to one another and create independent action based on processed data. Connected water, heating, cooling and electricity systems lead to massive productivity gains, especially when attached to a smart grid that can almost instantaneously scale electricity pricing and supply to meet demand. IoT can be used across all urban processes, such as water systems, which represent 25-40 percent of the total power usage within urban areas.

A recent project in Fortaleza Brazil focused on rightsizing pumps in the municipal water supply and implementing an automatic control system. This project cost the government $1.1 Million but led to savings of $2.5 Million or 88GWh of electricity over the first four years it was in operation. Additionally, the water authority was able to add 88,000 new connections since their new system was smart and therefore scalable. Another project in Aarhus, Denmark implemented electricity generation in its wastewater treatment facilities. After installation, this system produced 90 percent more electricity than what was needed to run the plant. IoT isn’t just limited to large scale infrastructural investments. It can also extend to private homes, where water heaters that run when energy is cheap or localized power storage units will allow for the use of electrical equipment such as smart washing machines during hours of peak electricity prices while paying non-peak costs. These solutions will add to the overall efficiency of our urban power systems and also flatten costs, providing an economic boost.

Other urban applications of IoT include the monitoring of greenhouse gas emissions at a hyper-specific local scale. By distributing sensors across the city in places like signposts and traffic lights, the city officials would have consistently updated information about the ecological health of the city and would be able to rapidly act on any gas leakage or other potential health hazards. IoT enabled smart grids allow consumers to manage their own personal usage with greater access to information, minimizing the knowledge barrier typically associated with high or inefficient energy use. Additionally, smart monitors allow for consistent monitoring of a building’s mechanical, electrical and plumbing (MEP) systems by way of a building management system (BMS) which could automatically shut down any service if a leak or inefficiency is detected. The data created by these sensors could then also be analyzed to provide the system’s designers with data on energy use and inform future grid enhancements, creating a consistent feedback loop that will bring future infrastructure closer towards maximal efficiency.