THE FUTURE OF SMART POWER FOR BUILDINGS
The future is Direct Current – DC. Electrical power storage and solar power generation, which are both growing at unprecedented rates, deliver power through DC. Most of our electrical appliances, both at home and at the office, also use DC. Still, because the power grid supplies AC power to households, electricity from battery storages or PV has to be converted to AC and then back to DC before it can be used in households or office buildings. While high-end AC/DC converters used for battery storage and PV typically loose 3-6 % of the electricity in the conversion, standard consumer electronic converters and LED-drivers have losses of up to 25 %. We would do both ourselves and the environment a favour by skipping the AC conversion, especially for buildings with local generation of renewable energy and energy storage. But is this realistic? And what tools and technologies will be needed for this to happen?
Due to lack of standardization of Direct Current (DC) voltages for electrical appliances and LED lighting in both public and private buildings, each appliance comes with its own power adapter for transforming Alternating Current (AC) voltage from the electrical grid to DC voltage used in these appliances. The range of DC voltages typically varies from 5 V to 20 V, while the power consumption seldom exceed 100W, e.g. when charging a high-end laptop. Power adapters used are often low-cost and thus ineffective leading to heat losses and dissipation of useful energy. Consumers also need different adapters for e.g. their laptop, speakers and power tools – and for some appliances, the same adapters cannot even be used for different generations of the same product.
The figure above shows a building supplied by an AC grid and local PV, with a number of typical electrical appliances. As the appliances use DC, power from the grid has to be converted from AC to DC for each separate appliance. For the power generated by the PV modules, it must first be converted from DC to AC and then back to DC to be usable in the appliances. Power usage would clearly be more efficient with local DC grids in buildings – i.e., skipping the AC conversion steps and using only DC converters for power from the PV modules. However, for this to happen there is an evident need for standardization of adapters and chargers.
The USB Type-C (or short USB-C) contact, which was introduced in the market in 2015, makes it possible to use one adapter for a large number of low voltage electrical appliances – not only mobile phones and computers but also TV:s, LED devices, building automation and more, as shown in figure 2 below. One essential features of USB-C is that a port can provide any voltage between between 5-20 V and up to 100W, allowing for power supply to a wide array of different devices. In short, it is one multi-purpose adapter which benefits end-users through simplicity.
USB-C - A NEW STANDARD FOR DC
However, besides the element of simplicity and convenience, there are more benefits to the USB-C contact. The seemingly greatest benefit of USB-C is that it allows for bi-directional energy flow without any need for changing cables or reconnecting between ports. This means that any battery can deliver energy not only to its appliance, but also back to the electrical grid – every device with a battery becomes an energy storage on micro-level. Also, by using USB-C, charging speed can be varied and controlled which means that for instance it is possible to synchronize charging with the availability of local PV production. All loads supplied through USB-C are essentially “controllable loads”. Through the USB Power Delivery standard, negotiation of power direction, voltage level, current level and communication of battery status, the benefits of USB-C extend to more than just simplicity.
SMART GRID APPLICATIONS
The USB-C standard has many potential benefits, not the least on an aggregated level and especially when it comes to smart grid applications. Energy storages are key to future energy systems with increased integration of renewables. Today, most of these are either large-scale grid-connected energy storages or medium-scale residential energy storages. While the first is intended as back-up power for grid owners or industries, the latter is often used for storing energy from intermittent sources, e.g. wind or solar. However, as the number of small-scale battery powered appliances in homes and offices will continue to increase in the near future, it would be wasteful not to integrate these into the smart grid as well. USB-C could, as we have seen, play an important part in this – with an estimated 3 billion devices globally being connected through USB-C in 2019, there is a lot of energy that can be supplied to the grid if needed. Still, the energy flows need to be controlled and aggregated before the impact of USB-C on smart grid development can be utilized properly. This is where Ochno’s Cloud Socket comes in.
Ochno Cloud Socket, illustrated in figure 3 above, is a hub-based solution designed for office buildings, public buildings or households. By plugging a USB-C device into a contact in a wall, a table or virtually anywhere in the building, that device becomes connected to the building. Ochno technology then allows for monitoring and control of power supply to and from all USB-C connected appliances and batteries through negotiated capabilities. If a device is in need of power, it is supplied as usual but with the possibility of adjustable power flow. If there is an excess of power in USB-C devices, the power flow can be reversed and they can supply power to the grid or other parts of the building. Also, any devices that is connected such as a LED lamp or a camera is basically a standard USB-device which allow it to also be fully controlled and communicated with the same cable that supplies the power. This removes the need for other smart-building infrastructures such as DALI, KNX or even Ethernet. This is all controlled through one central cloud system using the Ochno Cloud Socket.
In short, small scale distributed energy storages can become a reality by using Ochno technology. No significant investements are needed, since the energy storages – batteries in electrical appliances – are already installed and in use all over the world. They simply need to be connected. The number of battery-powered devices globally is already large and will continue to increase, and USB-C will be the standard to connect and charge these. Ochno also adds the possibility of load control of devices, especially LED, which gives public buildings and households the opportunity to become real “smart buildings” and in a longer perspective an integral part of large scale smart grids. Ochno technology takes us one step closer to using the power that we have available as efficiently as possible.