Smart Cities

As a power supply manufacturer of efficient, compact power supplies, RECOM is well-positioned to support the smart technologies that go into the making of a smart city.

can, for example, adaptively control and direct the internal lighting and HVAC (Heating, Ventilation, and Air Conditioning) systems to keep the air fresh, the room temperature comfortable, and the lighting levels adequate. If an office or meeting room is unoccupied, then the lighting can be automatically switched off, the airflow reduced, and the temperature less precisely controlled to reduce energy costs. To augment the workers’ comfort, each work space can be individually adjusted for ambient lighting levels or temperature (women prefer warmer surroundings than men do). Even the color and temperature of the lighting can be automatically adjusted to match the diurnal variation, to feel less artificial, or to improve productivity. The ventilation can be lowered to reduce drafts. Alternatively, in a crowded area, air circulation and filtration can be intensified to reduce odors or the chance of air-borne infection.

The building management system (BMS) is the central computer system that collates all the occupancy, temperature, air-flow, ambient light, and volatile organic compound (VOC) sensor data and uses it to control the various actuators, fans, vents, and LED lighting gear, according to the individual settings. The BMS also coordinates with the other facets of an intelligent building, such as access control, security, communications, and smart energy usage.

RECOM offers a vast range of both DC/DC and AC/DC converters that can power these smart systems, actuators, and gateways, from a few watts up to kilowatts. The main statutory requirements are that the power supplies in the BMS systems must comply with the IEC/EN 60335-1 “Household and similar appliances” safety standard, meet the EN 55014-1/-2 “Electromagnetic compatibility emission/susceptibility” limits, and be additionally tested for compliance with the EN 62233 standard “Electromagnetic fields… with regard to human exposure” limits. This implies that not all commercially available power supplies are suitable for smart buildings, and the certification and compliance documents need to be checked carefully.

Large buildings need a lot of energy, so they are often fed with three-phase electricity. For 230V AC wall socket systems, the main supply is typically 415V AC, as 230V AC is the phase-to-phase voltage. In countries using 115 VAC wall sockets, the 3PH supply is typically 480V AC, and sub-transformers are used to generate the 115V wall socket voltages wherever needed. However, one trap for the unwary is that the lighting systems in large buildings are commonly powered from between two of the 480V AC phases – in other words, the lighting gear is run from a 277 VAC nominal supply voltage and the auxiliary power supplies for occupancy, ambient light, or remote control receivers need to be certified to operate at up to 305V AC peak voltage (277V + 10%). RECOM offers a range of “/277”-type certified power supplies that have been UL-certified for this peak input voltage, as well as operating down to 85VAC input allowing 115V, 230V, 240 V, or 277V AC supplies to be used. RECOM also offers “/480”-type AC/DC converters with an extra-wide input voltage range of 85–528V AC, accommodating all possible nominal supply voltages from 100V AC up to 480V AC.

A smart building is only as good as its data, so to ensure complete coverage, each room or space could have multiple sensors, controls, and information displays. Several communication protocols are available, such as WLAN, KNX, DALI, Zigbee, or BACnet, with gateways to allow different systems to communicate with each other and share data across the network. Each module gateway or interface needs a power supply, which is often bus-powered.

RECOM offers a wide range of highly efficient, compact, board-mounted switching regulator modules with 5V, 12V, 24V, or 48VDC nominal input voltage. With so many complex interconnected systems, using isolated DC/DC converters in a BMS is often useful to block cross-interference, to ensure that faults do not destroy the whole system, or to allow for differing ground potentials. Again, RECOM has a wide range of isolated DC/DC converters suitable for bus and signal isolation in a variety of form factors (low profile, SMD, or THT, etc.) with 3kVDC, 4kVDC, 8kVDC, or 5kVAC isolation withstand voltages. Uniquely, RECOM also offers the RHV2/RHV3 range with an impressive 20kVDC isolation between input and output, ideal for monitoring the high voltage electrostatic screens in HVAC air filters.

Like smart buildings, smart energy attempts to balance out the energy needs of a city to make optimum use of its resources by redirecting the flow of power throughout the city. A smart city has multiple energy sources including renewables such as solar, wind, hydrogen, and geothermal, as well as conventional electrical power generators. On a more local level, a smart building may have wind generators and solar panels mounted on the roof, which can supply some of its needs during peak demand times, while feeding the energy back into the grid when a surplus is generated. Smart energy allows more efficient grid management, optimizing the power generated by each individual source and distributing it where it is most needed, while simultaneously lowering overall costs and reducing pollution.

The key to a well-functioning smart energy system is a smart grid equipped with smart meters, outage detection, and energy usage monitoring, reporting back continuously to the utilities. Real-time data also allows users to control their energy costs, allowing them to defer the switching on of any high-power equipment or machinery when the energy cost is high to a later time, when the demand is lower and, therefore, the price is lower (dynamic energy pricing).

RECOM makes several AC/DC and DC/DC converter families that have been used in smart meter and smart grid applications. The relevant safety standard is UL/IEC/EN 61010-1 “Safety requirements for electrical equipment for measurement, control, and laboratory use.” Such DC/DC converters isolate the low-voltage power supply for the current, voltage, and phase sensors crucial to the functioning of the monitoring equipment or the photovoltaic inverters used to convert the DC generated by the solar panels into AC.

Additionally, for AC/DC converters powered directly from the grid, the over-voltage category (OVC) is important, as defined by the IEC 60204-1 standard. For any power supply hard-wired to the mains in the electrical cabinet, OVC III applies, meaning that the converter must withstand 4kVAC transients caused by lightning strikes, as well as having increased creepage and clearance separation distances for added safety. RECOM offers five different compact OVC III compliant AC/DC products in the range from 3W up to 40W.

This area is the most rapidly developing smart city technology, driven by the pressing problems of traffic congestion, parking, and goods deliveries in many city and urban areas. Many large cities (London, Singapore, San Diego, and Milan – to name a few) have already introduced congestion charges to try to dissuade car drivers from entering the city centers during peak hours, but a smart city would be able to eliminate city center personal transport completely, offering low cost, flexible, and readily-available public transport or cycle lanes instead. As most people desire a quiet, clean, safe, and pollution-free city center, smart mobility would have the largest impact on the lives of the citizens.

Even if pollution-free electric vehicles (EV) are permitted in the city centers, smart parking apps would reduce the time spent searching for a parking spot or a charging point. Parking spots could be allocated dynamically, disappearing on busy thoroughfares during the day to improve traffic flow, but reappearing in the evening to allow more easy travel to theatres, restaurants, and nightspots.

Outside of the city centers, intelligent traffic lights and smart speed limits would be used to dynamically control and prioritize the traffic flow for optimal journey times, or to reduce the risk of accidents. The main goals of smart mobility are to allow people and goods to move freely within the city, while simultaneously reducing air pollution and vehicle-related injuries or deaths.

Like smart buildings, smart mobility relies on heavily networked sensors, cameras, and information displays, all of which need compact, low, and efficient power supplies to supply the sensors, transmitters, and data links that constitute the system. For example, RECOM’s RAC15 series has been developed with chamfered corners, a minor modification that allows it to better fit inside circular or cylindrical mast-heads, often used in street lighting or street camera installations. The power was chosen to be sufficient to supply sensor and video monitoring equipment with enough reserve for a long-range radio link.

Besides the city traffic monitoring and control infrastructure, a smart city would also feature sufficient EV charging points for all of the electric cars, e-bikes, cargo bikes, and electric delivery trucks needed. The EV charging points would be bi-directional, allowing the smart energy grid to tap into the combined stored electrical power of the connected EV batteries during peak demand, while still ensuring that the EV drivers still had enough charge to travel to their homes. RECOM has many products ideal for unidirectional or bidirectional EV chargers – especially for the isolated DC/DC power supplies needed for the high-side switching transistor gate drivers. Additionally, RECOM offers AC/DC converters for auxiliary supplies and isolated DC/DC converters for the CAN-bus interfaces and battery performance monitoring in the vehicle’s high voltage battery monitoring system, as well as on-board battery chargers.

Smart cities will also make more use of light rail urban transport systems to move people around more efficiently and quietly. Electric trams and buses that are charged at each stop and that can then move to the next station without the clutter of overhead wires have already been introduced in cities such as Seville, Bergen, Oklahoma City, and Florence, while London has chosen hydrogen-powered buses. RECOM makes converters for the battery management systems and fuel cells in these vehicles, so we can play our part in smart mobility.

Just as smart mobility will have the most visible impact of all of the smart city technologies, smart data will be the least obvious, but it is still an essential part of the whole picture. The massive amount of data collected by a smart city must be sorted, filtered, and analyzed in real-time if it is to be useful, all the time being protected from misuse with proper security and privacy controls. A deeper analysis of current trends, patterns, and people’s interactions with the city will reveal new insights and allow progressively better implementation of the city infrastructure, with faster reaction times to problems. Predictive analysis will make long-term future planning more ecologically-sound, productive, and fit for purpose.

The key enabling technologies for smart data are IPv6 and 5G. IPv6 is an internet protocol that allows up to 2128 individual addresses, allowing much more than billions of billions of billions of sensors to be uniquely addressed (theoretically, every atom on the surface of the Earth could be uniquely addressed, and there would still be spare address capacity for a further 100 Earths). Fifth-generation (5G) cellular communications employ GHz frequencies allowing up to 4Gbit/s download speeds, the kind of information transfer rates needed to handle the massive datasets generated by a smart city.

Despite its advanced performance, a 5G modem micro-cell needs only 10W of electrical power to cover a radius of up to 2km or 2000 simultaneous users, and the antennas can be inconspicuously mounted on the top of the street lighting poles, for example.

RECOM offers a wide range of high-power density AC/DC and DC/DC power supply modules suitable for powering compact 5G modems.