>>219550Update.
I made a quick heating system with this old hair dryer and base board heater thermostat. I set the hair dryer on low and set the thermostat to 60F. At around dark the system kicked on 2 hours after the sun was no longer shining directly on the tunnel. This morning it was 22F outside and 52F inside. The hair dryer ran until just now at 10am when it shut off. The temps inside the tunnel when it shut off were 72F and outside 37F. The thermostat is located near the soil and the thermometer I read is partway towards the top of the tunnel.
