Exercise EE1-02.03 – Plant lighting, power and efficiency

Prof. Dr. Thorsten Jungmann (last updated 2025-10-21)

Relates to EE1-02 Electrical quantities and units, terms, symbols and models

Task

A passively cooled LED lamp for plant lighting with a rated power of $P=300\mathrm{W}$ is connected to a standard household socket-outlet. Its efficiency is specified as $\eta =0.35$.

a) How large is the power that the lamp gives off as heat?

b) What current flows through the supply cable of the socket-outlet when two lamps are operated on a multiple socket-outlet with supply cable?

c) What is the cost of operating two of these lamps for one year with a lighting cycle of 18/6 (18 hours of light, 6 hours of darkness)? Assume an energy price of $40ct/kWh$.

Solution

a) $195\mathrm{W}$
b) $2.61\mathrm{A}$
c) $1577\mathrm{EUR}$

▶️ Full worked solution