The Application Study in Solar Energy Technology for Highway Service Area: A Case Study of West Lushan Highway Low-Carbon Service Area in China

Table 2

The comparison of recommended operating mode of solar heating water system for highway service area.

Operating conditions	Operating mode
	Natural circulation	Direct circulation	Forced circulation
Instability water pressure	Available	Unavailable (1)	Available
Insufficient power supply	Available	Unavailable (2)	Unavailable (3)
Instant hot water	Unavailable	Available	Unavailable
The relative installation location of collector and storage tank
High collector	Unavailable	Available	Available
High storage tank	Available	Available	Available
Operating temperature
Above 0°C	Available	Available	Available
Below 0°C	Available with antifreezing measures

(1) Available with thermostat control pump.
(2) Available with thermostatic valve.
(3) Available with DC pump under photoelectric cell.