Adding solar energy to a building’s energy mix is a crucial aspect in making a building more energy independent; however, it is only the first step.
As the world is moving towards sustainability and energy independence, so too is building architecture beginning to change to incorporate these values. More frequently we are seeing net-zero buildings and green building rating systems, such as Leadership in Energy and Environmental Design (LEED). In parallel, commercial buildings are becoming smarter. This has opened the way towards managing energy in a more efficient manner.
One of the ways to better manage energy is to design buildings that require less energy, for example by using passive ventilation techniques, passive solar energy, double/triple pane glass and thermal mass material so that the requirement for HVAC units is reduced and sometimes even eliminated. There are many other areas in which building designs can decrease the energy requirements of a building, from energy-efficient lighting, passive lighting, water conservation, and more. Yet, no matter how much a home or a commercial building is able to reduce its energy requirements, it is nearly impossible to completely eliminate energy demand. However, the building can become its own energy generator.
Power in the Hands of the People
One of the most promising aspects of solar energy, versus other types of renewable energy, is that it is designed to be a distributed power source. Almost anybody with a roof has the potential to install their very own energy generation system. It truly places power into the hands of the people. For commercial buildings with large rooftops, as well as homes, adding a photovoltaic (PV) system can be an excellent way to produce the amount of energy that is consumed on-site. However, for high-rise office buildings and apartment buildings this can be more difficult.
For instance, the University of Technology Vienna (TU Wien), as part of its green building initiative, renovated its former chemistry building with the goal of becoming the first energy-plus commercial high-rise building. This was a lofty goal as high-rises are particularly challenging for PV to meet energy demand since roof space is limited compared to energy consumption. To overcome this challenge, innovative design planning was required, and a building-integrated system was conceived.
Leveraging the design flexibility offered by a DC-optimized solution was fundamental in increasing system production and size by allowing the entire building’s surface to be covered in solar modules, while also optimizing each individual panel. At the time of completion, the system was thought to be Austria’s largest Integrated PV site and the direct environmental benefits of the PV system were calculated to be equal to >54,000 kg of CO2 emissions saved, which is the equivalent of nearly 200 trees planted or nearly 420,000 lightbulbs powered for a day.
However, while adding solar energy to a building’s energy mix is a crucial aspect in making a building more energy independent, it is only the first step. The next step is improving the management of that energy in order to increase self-consumption. This is because energy usage does not always align with the energy generation of a PV system. As such, there are two ways that the energy can be managed to overcome this inconsistency. The first technique is energy storage and the second is consumption shifting.
Energy storage is an essential part of smart energy management as it stores energy when it is produced for consumption at a later time instead of either limiting energy production or feeding it into the grid. With PV+storage systems, the inverter is responsible for managing battery charge and discharge patterns to meet consumption needs and reduce the amount of power purchased from the grid. The graph below shows how energy storage is able to increase self-consumption and energy independence in a typical residential PV installation.
For example, in time-of-use (TOU) markets like California, energy storage can protect consumers from higher rates during peak periods when PV systems are likely to be producing little or no energy. Excess PV energy generated during the day can be stored in a battery and used in place of electricity from the grid during the evening, when tariff charges are typically higher.
Shifting energy consumption is another form of energy management that can also increase self-consumption. This technique combines the technology of smart buildings with PV energy. By merging these two technologies, smart energy management solutions can automatically use a PV system’s excess power to increase solar energy usage, help lower electricity bills, increase energy independence, and provide greater convenience. Devices and appliances, such as immersion heaters, lighting, fans, and pool pumps, can be controlled by smart energy management solutions that include AC switches with a meter and plug-in sockets with a meter, and dry contact switches. With the immersion heater, excess PV energy can be directed towards water heating, which is a low-cost form of energy storage. While the other devices allow appliances, such as pool pumps, fans, cold-storage, thermostats, and lighting, to be remotely controlled and utilized during high PV production for increased self-consumption.
In addition to increasing energy independence, smart energy management allows for a simple user experience when combined into one integrated energy management and monitoring platform. This enables a more streamlined smart energy and building management process to reduce operation and maintenance costs.
As the technology advances, we will continue to see more opportunities to further integrate it into making buildings more energy efficient. For example, weather and irradiance forecasting integrated into energy management systems can help ensure more efficient planning of building heating, or personalized profiles and thermostat controls that can help increase comfort without additional resources. Combining these types of technology with architectural designs can help our buildings exist in better harmony within their surroundings and environment.
Magnus Asbo is senior director of residential technical marketing at SolarEdge in Milpitas, CA. He can be reached at [email protected]. This is his first article for Facilities Manager.