By Dan Robertson
Rental centers with solar LED light towers in their fleet can offer customers a valuable alternative to diesel- powered light towers. Construction projects involving night-time operations or security lighting have historically used portable diesel powered light plants. These towers require con- tractors to not only keep the engine fueled, but to invest labor in fuel-runs and trips to turn engines/lights on every night and off every morning. The long engine run time (eight to 14 hours nightly) not only requires fuel, but also requires a rental company to provide routine diesel engine maintenance and to replace metal halide lights frequently.
Solar LED light towers, first introduced by Progress Solar Solutions, LLC in 2010, are being steadily adopted into fleets by most of the leading national and regional rental equipment chains, as well as by a growing number of independent and specialty rental stores. This new generation of light towers has been expanded and consistently improved to include units powered by 100% solar or solar/ wind-powered renewable energy and, most recently, by solar/hybrid light towers that combine solar renewable power with a backup propane (dual fuel) clean energy generator. These light towers can perform year-round anywhere in the country without any downside to diesel-powered towers.
Change in light tower routine
A typical construction project has many light towers positioned throughout a job site to provide working light where needed and to improve safety and security for employees and equipment. Historically, diesel light plants are often rented and delivered on site. The lights typically require contractor personnel or a separate fueling service to purchase and transport fuel, refueling each unit every couple of days. In addition, contractor personnel invest time each evening to turn the diesel engine/lights on, then turning them off again in the morning. At times, units may not be turned off and will run until the fuel is exhausted. Often, because of the noise and exhaust, diesel units are positioned off to the side of the work area that needs light.
Solar or solar/hybrid-powered light towers can be positioned right where the light is needed because there typically is no or limited noise and no exhaust fumes or carbon emissions during operation. The lights are turned on/off by automated timers at user-designated times. For the Progress Solar/Hybrid (SHyb1000) units specifically, the 1000 watts of solar power typically is sufficient to power jobs that run five nights per week anywhere in the country. Where crews need lighting seven nights of the week, these units will generate approximately 80-85% (depending on weather and use) or more of the power from solar renewable energy and the balance either from the onboard auto-start/stop propane generator or from an AC outlet to recharge the batteries.
Solar and solar/hybrid light towers use energy-efficient LED floodlights instead of the metal halide lights typically used on diesel units. The majority of the power (wattage) used in metal halide lights generates heat with a relatively small percentage going to generate light. Solid-state LED lights generate limited heat and the majority of its power is directly used to generate brilliant white lighting for job sites. Many of the diesel light tower manufacturers have begun converting or offering an option for LED lighting to take advantage of this new technology.
There are some significant differences in LED lighting and several variables such as lumen output-per- watt (LM/W), the beam angles and the color of light that determine light quality. The initial lumen output has essentially doubled – from 80 LM/W to 155 LM/W — in LED floodlights over the last several. Progress Solar now offers the first variable intensity LED flood lights on the market. They allow end-users to adjust the lights to high, medium or low, depending on the light level needs. For most projects a one-(diesel) to-one (solar/ hybrid) exchange is typical when using the Progress Solar/Hybrid with the variable intensity LED lighting. Vendors can provide IES files upon request for lighting engineers to optimize lighting based on needs.
Other benefits of solid-state LED lights include:
- Five to 10 times longer life than a metal halide
- Instant-on to full intensity lighting (no five to 10 minute warm-up required)
- Solid-state LED lights are more vibration-resistant than metal halides, making LEDs better for use on portable light plants
- Bright white LED lighting is ideal for use wherever video cameras are in operation.
Reduced environmental impact
A typical 6kW diesel light tower uses .75 gal/hr of fuel and generates 17 pounds of carbon dioxide per hour. If you run it for 12 hours per night, five nights per week, it produces 201 pounds of carbon dioxide nightly and 26 metric tons annually.
That greenhouse gas output is equal to what 5.5 cars produce. Used daily, it produces 37 metric tons during the year – equal to the greenhouse gas generated by 7.7 cars.
By comparison, one Progress So- lar/Hybrid 1000 LT on the “medium” light setting generates the majority of its power from solar renewable energy with no direct cost or carbon emissions. So, it will operate five nights per week with no carbon dioxide output, no greenhouse gas output.
Used seven nights per week for a year, it’s estimated that 80 to 90 per- cent of its power will come from solar. The balance comes from the propane generator. Propane is a cleaner fuel source than diesel and the backup propane generator uses about .75 gal/hr. At that rate, it produces 14 pounds of carbon dioxide per hour. Over the course of a year, operating every day and assuming it is running 20 percent of the time the lights are on, it produces about six tons of carbon dioxide. That equal to the greenhouse gas output of 1.3 cars.
What all this means is that converting from one diesel tower to a solar/ hybrid tower such as ours, operating daily for a year, and you’re eliminating the annual greenhouse gas output of
6.4 passenger cars – 31 fewer tons of carbon dioxide impact per year.
Source: epa greenhouse gas equivalencies calculator used to establish estimate.
A solar/hybrid light tower will have higher acquisition cost than a typical diesel-powered light tower. While this will lead to a higher rental rate, total costs to your customers will be lower.
Let’s assume a diesel tower will rent for $400 to $800 per month, with potential surcharges for total hours of use, and your customer uses it 12 hours each night for 30 nights. If diesel fuel costs $4 per gallon and the engine uses .75 gallons per hour, that adds $1,080 per month cost on top of the rental rate. Add in labor to purchase, transport and refuel, estimating a cost of $3 per gallon and 270 gallons for the month, that’s another $810. Total operating costs add, in this scenario, $1,890 per month on top of the rental rate. A solar/hybrid light tower typically will have a rental rate of $900 to $1,500/month, but it eliminates or minimizes any operating costs. If it uses propane as back-up, the estimated fuel cost for month is less than $400. Just for quick comparison, then, use the lower monthly rental rates. The diesel unit at $400 rental and $1,890 in operating costs comes in at $2,290 per month. The solar/hybrid tower at $900 rental and $400 per month for propane, if needed, totals $1,300. That’s a savings of about $1,000 per month per light tower for your customer. Obviously, there will be variations in rates around the country, but plug in your rental rates for a diesel light tower, plus fuel and labor costs, and estimate the monthly total for your customers. With an investment in solar/hybrid light towers, not only will your customers be able to promote their efforts to reduce environmental impact, they’ll be saving money.
Dan Robertson is the co-founder and a partner in Progress Solar Solutions, LLC. The company manufactures Progress Solar, Progress Solar/ Wind and Progress Solar/Hybrid Light Towers. www.ProgressSolar.com