Team Sustain | Integrated Energy Storage Enclosure

TeamSustain has developed a unique climate-controlled cabinet or enclosure to house the battery called as IESE, which stands for Integrated Energy Storage Enclosure, in which passive cooling is employed to maintain the temperature inside at about 28°C. The climate-controlled battery enclosure also features a battery water reservoir and tubing with mechanical automatic floats for easy watering, sensors to monitor temperature, voltage and current, and a communication bus incorporated inside the combiner box to transfer the collected data to the remote servers. The newly proposed system has a slanting corrugated roof for facilitating rainwater flow.

For remote Telecom towers or off-grid systems, reliable source of power is required. As electric power outages are undesirable, to ensure continuous power supply backup power supplies like lead acid batteries are used at base stations. These batteries at the base stations are housed in an enclosure. Batteries store electrical energy using chemical reaction and can be hazardous if they are improperly handled or contained.

Battery enclosures are made of different materials. Plastic battery enclosures are cheap, light and are corrosion resistant, but break down in sunlight and are not very strong. Wood is a good choice because it is non-conductive, and will prevent an electrical short from occurring between an exposed battery terminal or cable and the box. One shortcoming of using wood is that, over time, leaked or spilled battery electrolyte will undermine its structural integrity. Plywood is another material used to make enclosure, which is relatively light and strong, but the disadvantage is that it might rot if not protected. Usage of concrete for enclosure making is also suggested, as it results in structures which are very strong, and can be built underground in order to maintain steady temperatures. The major cons associated with these structures are that these structures are heavy.

Hydrogen venting is another prime issue concerned with battery enclosure. The main objectives of a ventilation system are management of environmental air temperature, humidity and air quality. The risk involved in a lead acid battery is explosion when charging exceeds 14 V (for a 12 V battery), and they begin to produce hydrogen and oxygen. The gas burns at a concentration of about 4% by volume when mixed with air. At concentrations exceeding 4% it results in invisible explosion. As hydrogen disperses rapidly, it has to be removed to prevent accumulation. Because hydrogen is “lighter than air and will tend to concentrate at ceiling level,” the National Electrical Code (NEC) suggests that “some form of ventilation should be provided at the upper portion of the structure. Most of the battery enclosures are provided with a vent at the top, so that the hydrogen inside the enclosure can be drained.

Chemical reactions internal to the battery are driven by voltage and temperature. Higher the battery temperature, faster the chemical reactions. While higher temperatures can provide improved discharge performance the increased rate of chemical reactions will result in a corresponding loss of battery life. Also operating batteries at higher temperatures can result in the shedding of active materials from the battery plates. The resulting sediment build up at the bottom of the case can lead to electrical short circuits.

Battery capacity is temporarily diminished at low ambient temperatures, and deeply discharged batteries housed in unconditioned enclosures in cold climates are vulnerable to freezing, which can result in cracked cases, spilled electrolyte, and destroyed batteries. The existing battery enclosures employ active cooling methods in order to reduce the temperature inside the enclosure. The active cooling methods are those which use powered devices such as fans or pumps for heat transfer. In some cases, active cooling methods are used in tandem with passive cooling to function more effectively. The proposed system employs passive cooling and passive hydrogen venting.