Central Bedfordshire approached us to provide and install solar powered parking lot lights for Houghton Hall Park in Dunstable, UK. The given requirements for the project were to mount the lights on 4 meter poles, use a PIR motion detector to dim the light level, power the lights for 4 hours past sunset and 2 before sunrise, and provide coverage for the parking lot and sidewalks around the site’s visitor center.
Due to the low solar conditions in the UK during winter time, our goal was to keep the LED power as low as possible. For many UK parking lots we use 10W or 15W LED fixtures, but due to the short illumination time, and implementation of dimming with a PIR, we were able to quote for higher than usual LED options.
To determine the appropriate LED power and number of light poles, we generated a photometric layout for the site. While creating the layout for the solar parking lot lights, careful attention was paid to the large trees to the east of the property. In order to avoid potential shading on the solar panels, light poles were positioned within the parking lot, rather than along the eastern perimeter. Lights were also positioned to achieve the most efficient coverage, as well as keeping any light pollution to the natural areas to a minimum.
We specified a quantity of nine light poles for the site. This included seven solar parking lot lights for the main parking area. These light poles feature a 20W LED with a mixture of type II and III optics. We have an additional two solar light poles to provide illumination for sidewalks and building entrances. The two additional poles feature 10W LEDs with type II and III optics. We achieved an average of 5 lux (.5 fc) throughout the site.
All nine solar parking lot lights were supplied with the same illumination schedule. The light poles will illuminate for 4 hours past sunset, and 2 before sunrise. Within that time frame the lights will be at 33% power, and switch to 100% power when motion is detected. The solar equipment includes an allowance of 2 hours at full power. With the full power mode lasting for 60 seconds, that equates 120 activations per evening. In addition, the battery capacity allows for at least three days of reserve power.
As with all our projects, the solar panel and battery configuration were based on the worst case scenario. For the UK, this means compensating for 16 hours of darkness with only 8 hours of daylight for the equipment to fully recharge. The 20W LED solar light poles were supplied with 140W solar panels, and two 32AH batteries. The 10W LED lights were supplied with 90W solar panels and two 18AH batteries.