In retail shops, two concepts are most often encountered: they can be found as smaller buildings, usually detached, with a sales area of up to 1000 m2, as well as large shopping centers with a dominant supermarket of 3000 m2 and other shops and services in the common hall. A separate chapter are the giant shopping centers, for example the Černý Most Center, Westfield Chodov shopping center, etc.
Retail stores have their specifics in terms of building management systems. The stores strive to standardize as much as possible so that construction works smoothly and without unnecessary changes. We perceive strong pressure on the price, everything unnecessary is excluded from the standards, the client focuses on the shortest payback period. This is also reflected in potential savings-funded projects (EPC, Energy Performance Contracting) – the maximum acceptable payback period does not exceed 6 years. The lifetime of the building is purposefully planned (remodeling takes place after about 15 years of operation) and operators are trying to install technologies whose lifetime corresponds to this horizon.
Heating is usually handled by an air handling unit, which is also used for ventilation. Underfloor heating is not used, although it would make sense considering the available low-potential waste heat from commercial cooling. The problem is that the sales area is occupied by shelves with goods, which both reduces the possible heating area, and on the other hand, the goods could lose their quality because of the heat. Often, the cash register area, which is usually near the entrance, is often discussed: previously, radiant panels were installed in this zone to achieve the comfort of cashiers. But they did not work well, because the radiant heat could not compensate for the cold air flowing from the entrance. The current solution consists in better air distribution in the area of cash registers together with hot air curtains. Ideally, however, would be the local heating directly in the cash booths. For larger shopping centers, the so-called mall, a hall with other smaller establishments such as tobacco, florist etc. helps. Thanks to its volume, Mall helps to protect the cash register zone from drafts.
The central air handling unit for the sales area is controlled by a time schedule according to the shop’s operating hours, often in combination with a fresh air regulation using CO2 sensor. The sensor is located in the exhaust or in the cash register zone. In CO2 regulation, the unit also has the function of heating and in winter operation it must operate in the circulation mode, so that the fresh air ratio is reduced to a hygienic minimum, but the flow rate at the supply line remains constant. This may be important for proper air distribution, especially when swirl diffusers are used. Sometimes an air quality sensor (mixed gas sensor) is used instead of the CO2 sensor, which also reacts to odors from animal feed and drugstores. The shop is relieved of this burden by morning ventilation just before the opening hours. In summer it is useful to use night ventilation, which pre-cool the sales area with cold night air at minimal cost.
Hot water heating is usually solved by local electric heating. Waste heat from commercial cooling can be used in case of higher consumption. Cooling system suppliers today offer combined systems with heat exchangers or even complete hot water preparation including reheating.
For cooling the sales area, warehouses and other operating areas either separate systems are used, similar to office buildings, or split air conditioning units, so popular for its simple assembly, low cost and easy billing (only electricity consumption is measured, tenants need not install calorimeters). Specialized suppliers of commercial refrigeration, however, also offer a comprehensive solution where heat pumps produce both refrigeration for food and air conditioning as well as heat for heating and hot water. These systems are more suitable for smaller, highly standardized stores. In large shopping centers, cooling production for air-conditioning is usually handled centrally, without any link to commercial cooling.
Lighting is a very important unit for retail. Insufficient lighting intensity can have a negative effect on the sale of goods, oversized bodies waste energy. That is why lighting was usually the first area to be reconstructed, and the lamp or fluorescent lamps were replaced by energy-saving lamps and later by LED lights. Traditionally, the lights on the sales area are managed in groups, approx. the third is switched by the time program as the first stage and the rest a few minutes before the start of the sales period. In places where daylight is also lit, it is worth installing dimmable bodies (eg. with DALI interface) and controlling them in addition to the time program also according to the outdoor light sensor. For large stores, up to 20 – 30 circuits are independently controlled by time programs, including outdoor advertising lighting, parking lots, ramps, etc. A typical shop with a sales area of about 3000 m2 thus contains about 800 – 1000 data points – inputs and outputs of the control system. The process stations are installed in 2 or 3 distribution boards, mostly located at a heat and cold source and in a low-voltage substation. The controllers, control panels and the central office are connected by a separate technological IP network.
As technologies such as cooling systems, air handling units, boilers and others are increasingly equipped with self-regulation, the measurement and control profession in standard smaller stores now focuses more on the integration of these technologies, their coordination, consumption measurement, data collection and their transfer to superior system. Usually, a single process station with several interfaces is sufficient, for example, a typical 1000 m2 shop usually uses a PLC with 4 serial communication ports and Ethernet – which is Domat mark320 or IPLC510.
The operation of the control system should be as simple as possible for the user. In smaller shops, it is not worth training any local staff, the systems are virtually unconfigurable, all technology is in charge of a dedicated team of technicians at the headquarters. They solve possible problems and requirements, if possible remotely thanks to central visualization (SCADA) and connection through the corporate network. Thanks to central data collection and high similarity of all shops it is possible to compare their consumption and energy efficiency (so-called benchmarking), also in relation to turnover, number of customers, etc. This applies not only to retail food stores, but also to hobbymarkets, building stores, etc. For the evaluation, specialized programs such as Domat ContPort are used. Up to several hundred shops are connected to the central office.
For large shopping centers, one local SCADA station is installed at the central control room of the building, which is used by maintenance personnel to deal with common operational situations, while long-term data evaluation is the responsibility of an energy specialist. They also negotiate energy purchases, solve, for example, optimum values of a quarter-hour maximum, and should provide management with suggestions for possible austerity measures.
Achieving comfortable living conditions in retail is also important to maximize sales. Store chain managers are aware of this and we could see the results of their work daily: a pleasantly air-conditioned shop in the hot summer, fruits, vegetables and meat lit with the right lighting, or the smell of fresh bread that spreads throughout the store. At the same time, it is desirable to operate the stores optimally – and this is also helped by a quality control system with a capable operator, who can evaluate the measured data and has sufficient powers to enforce austerity measures.