Energy and Natural Resources

Rayfrigeration: a Solar-Powered Transport Refrigeration Unit

12 October 2017

A zero-emissions Transport Refrigeration Unit (TRU) has completed a five-month trial on a truck delivering fresh dairy products throughout Fresno, Calif. TRUs are typically powered by high-polluting, small diesel engines to provide cooling needed to transport chilled products. The new system is solar-powered and achieved emission reductions of 98 percent nitrous oxide, 86 percent carbon dioxide and 97 percent particulate matter during the test period.

The “Rayfrigeration” TRU from eNow Ray features an 1,800 W solar system in combination with a Johnson Photovoltaic panels mounted on the dairy truck’s roof. (Source: eNow)Photovoltaic panels mounted on the dairy truck’s roof. (Source: eNow)Truck Bodies refrigeration unit and Emerson’s efficient compressor technology. The unit's cold plates and batteries are initially charged from utility power overnight, but while on a delivery route, power is provided by eNow’s solar photovoltaic panels mounted on the truck’s roof.

Designed to support medium-temperature refrigeration applications, the Rayfrigeration unit is also projected to reduce operations costs by up to 90 percent by eliminating diesel fuel and maintenance costs. An increase in battery life associated with consistent charge maintenance by eNow also contributes to reduced operating costs.

The solar-charging technology is available through eNow, which currently has more than 4,000 solar systems operating in the U.S. on Class 8 trucks, buses, emergency and utility vehicles. These installations support applications as diverse as heating and cooling, liftgates, wheelchair lifts, safety lights, telematics, and other transportation applications.

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Discussion – 3 comments

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Re: Rayfrigeration: a Solar-Powered Transport Refrigeration Unit
2017-Oct-13 11:20 PM

Interesting story, but a few things were left out.

The story says that emissions were reduced for 5 months of the year, but didn't say how the system would work for the other 7 months.

Like, what happens during the rainy season ? Or when there is snow or ice ?

Does the company need to have another set of trucks to make up for inclement weather ?

I would say that every bit helps, but it sounds like this application is best for a niche geographical operating market.

Re: Rayfrigeration: a Solar-Powered Transport Refrigeration Unit
In reply to #1
2017-Oct-14 11:52 AM

The system is set up in a way that the solar power is only supplemental to the charge that the battery bank receives while at the truck depot overnight; where it is plugged into municipal power to fully charge overnight. The unit will run a normal shift without the use of the solar panels, but the solar panels do increase the overall lifetime of the battery bank by keeping the charge topped off during the shift. Battery life suffers when the batteries are heavily discharged, which over time will happen as the batteries degrade. This degradation of the batteries is normal though, just as in a normal vehicle, the batteries become a maintenance item that must be replaced every few years. The savings in fuel though well outweighs the cost of these replacement batteries, as well as the cost of municipal power to charge the battery banks.

This test was conducted during the warmest months of the year, which as you point out is the best time for the solar panels, but is the most extreme conditions for the refrigeration system in terms of power required to keep the truck cold inside. The rest of the year, due to the reduced temperature outside, the solar panel charge becomes less necessary. As pointed out earlier though, the panels do provide a very valuable piece to keep the battery bank topped off all day to ensure the best overall total cost of ownership for the end user of the truck.

If there is something that blocks the panels entirely, rendering them ineffective, the unit still runs off the battery power. The unit also has what is called a eutectic plate, which is essentially a big cold pack that is cooled overnight which acts as a fail-safe in the event of battery bank failure. The control system is set up in a way to know when the battery bank is low, and will utilize a fan in combination with the cold plate to ensure that the food in the truck is safe until the shift is over. The remote monitoring system also sends out warnings of the required battery maintenance that is needed. Since the batteries are standard AGM batteries, they can be procured at any local auto parts supply store.

I hope this additional detail helps show what a leap this is in the technology of refrigerated trucks. I'm obviously close to the project, and would be happy to answer any questions that you may have about this great project! The project will continue as well for the next year, so the info that you want will become available from direct field testing soon!

Re: Rayfrigeration: a Solar-Powered Transport Refrigeration Unit
In reply to #2
2017-Oct-14 3:54 PM

Thanks for the update.

Systems such as this are three fold ( imo)

A. The use of existing technology and it's applications helps to gain the public's trust.

B. The technical development will certainly lead toward increasing economic benefits.

C. The gain in fuel efficiency will assist our country in financial as well as structural security.

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