unused heat

例句：

1. 1.The factory generates a lot of unused heat during the day.
   工厂在白天产生了大量的废热。
2. 2.The solar panels capture unused heat from the sun and convert it into electricity.
   太阳能板从太阳那里捕捉到废热，并将其转换为电能。
3. 3. The old building has a lot of unused heat that could be used for heating purposes.
   这座旧建筑有很多废热，可以用于供暖。