How Much Solar Power Do You Need to Light a Single Light Bulb?
When considering the amount of solar power needed to light a single light bulb, several factors come into play, including the wattage of the bulb and the duration for which it needs to be illuminated.
Direct Solar Power for Lighting
Let's assume you want to directly light a 10-watt LED bulb inside a shed only while the sun is up. A 100-watt solar panel is capable of providing more than 10 watts of power from around 8 AM to almost 7 PM in the summer on a clear day. However, during this period, a current limiting circuit is necessary to prevent damage to the LED if the sunlight ever drops below 10 watts.
Outside of that time span, the LED will not receive enough power to light up, and it might also turn off if there is a shadow on the solar panel. This is why 'solar lights' often incorporate a rechargeable battery; the solar panel charges the battery during the day, and the battery powers the LED at night.
Calculating Solar Requirements
To determine the exact amount of solar power required, you need to consider the daily sun exposure and the power consumption of the light bulb. On a bad overcast winter day, a 100-watt solar panel might generate 1 sun hour (100 watt-hours) of electricity. However, on a good sunny day, it could generate up to 600 watt-hours. For the sake of this calculation, let's use the lower figure, 100 watt-hours, to estimate daily usage.
A 10-watt LED bulb will use 100 watt-hours of energy to run for 10 hours at full power. This means you could theoretically keep the LED lit for 24 hours a day with just 2.5 sun hours of good exposure, provided there are no shadows on the solar panel and the correct angle is maintained for optimal sunlight.
Storage and Battery Needs
To maintain consistent lighting, a stable battery is essential. For a 10-watt LED system, a 500 watt-hour battery would be adequate, assuming a 12-volt system. This equates to approximately 42 amp hours. While this may seem like a significant requirement, it's important to note that 10 watts of LED light is a substantial amount of light. Most 10-watt LED bulbs will emit around 800 lumens, which is quite bright for interior use.
If your setup is for lighting inside a camper, it's more likely to use five separate 2-watt LEDs to provide light in different areas. A decent 100-watt solar panel would be a little more than half a square meter in size. If the lights are not used all day and you are in a sunny location, this setup will run much more than 10 watts of LEDs.
By ensuring a proper setup with a correctly sized solar panel and appropriate battery storage, you can achieve reliable and efficient lighting with minimal energy input.