Building hot water demands
The barracks and dining facilities are large DHW users. The estimated DHW needs for a barracks building is 30 gal (114 L) of hot water per soldier per day at a temperature of 140 °F (60 °C). Most soldiers take two showers per day and one of them is in the morning, from 7:30 am to 8:00 am. To handle this peak usage DHW is stored in a tank having the size of ~22.5 gal (85 L) per soldier. Figure 4.2 graphs the heating rate throughout a typical week for a person’s DHW use in a barracks. Such a high DHW heating energy use makes a barracks a good candidate for a central solar hot water system.
The other building in the cluster that should be included in the central solar hot water system is the dining facility. Figure 4.3 graphs DHW heating energy needs. Typically, these facilities are occupied from 5:30 am to 7:30 pm. Three meals are served per day – breakfast (7:30 to 9:00 am), lunch (11:00 am to 1:00 pm) and supper (5:00 pm to 6:30 pm). The schedule will change slightly on the weekend. The hot water use of this facility is ~2.4 gal (9 L) per meal served. Assume that a dining facility of this size would serve 7500 meals each day.
The office buildings have a hot water use of ~1 gal (3.79 L) per person per day. If the occupancy of the building is not known, use 100 sq ft (9.3 m2) per person.
Another source for domestic hot water use is provided by NREL (shown below). Some guideline for determining hot water loads for sizing commercial SHW systems are:
- Apartments: 20 gal (76 L) /day of 120 °F (49 °C) set temperature water per bedroom
- Hotels/Motels: 15 gal (57 L)/day of 125 °F (51.67 °C) set temperature water per room
- Laundries: 20 gal/10 lb (76 L/4.5kg). wash of 130 °F (54 °C) set temperature water
- Restaurants: 24 gal (91 L)/day of 140 °F (60 °C) set temperature water per 10 full meals served
- Retirement Homes: 18 gal (68 L)/day of 120 °F (49 °C) set temperature per room
- Office Buildings (without showers): 1 gal (3.79 L)/day of 120 °F (49 °C) set temperature 0water per person.