Many portable DMS (Dynamic Message Signs) are already powered by Solar on our roads but very few permanent DMS. Numerous misunderstanding still exists especially regarding the size of DMS that can be powered by solar, the maintenance of the system, the battery life, and the longevity of the solution.
1. Solar Powered Dynamic Message Signs do not operate 24/7 = WRONG
Solar power signs operate with Solar Panels and batteries. The principle is very simple: The solar panels power the equipment and charge batteries when they can produce enough energy, when they cannot, the energy is provided by the batteries. In short, during the day the power comes from the solar panels and from the batteries during the night.
To make sure the system works 24/7, you must do an elaborate system calculation to correctly size the solar panels and the batteries, both must be sized correctly for a given system and location. For example, there is no point over sizing the solar panels if you under size the batteries.
Most systems are correctly sized, but we have seen mistakes that can lead to underperfomance of the equipment. So make sure you have experts calculating the system and that the system is calculated as per the location and the amount of sunlight per year with a focus on the worst month of with the amount of sunlight.
Will the system work if there is no sun?
Solar panels do not need to have full bright sunlight to produce energy: they work even when the weather is overcast. They may not produce enough energy to power the equipment but the batteries will complement the panels and provide the missing energy. It ultimately comes down to the right sizing, and taking into account the less sunny months of the year. Solar Powered Signs will also work well even under heavy rainfall.
2. Solar Powered DMS are Small Because Solar Power Systems are Too Big to be Installed on Road Side = WRONG
Solar Power system are proportional to the DMS power needed. So the bigger the DMS, the larger the solar chain needs to be. The challenge is to reduce the power needs in order to reduce the size of the solar system. This is why it is important to invest in Research and Development to engineer energy efficient products. If you have energy efficient DMS, then the solar system is of reasonable size and can be installed on the road side even for large DMS.
SESA SolarSign is a perfect example of ultra efficient DMS retrofit powered by solar systems. These DMS consume up to 5 times less energy than power grid DMS thus making the entire solution of reasonable size and affordable. Learn how txDOT saved over $8 million using DMS retrofit upgrades.
3- Solar Powered DMS are less visible than regular DMS = WRONG
Sometimes we hear that solar DMS cannot achieve the same performances than power grid DMS. Again, it all depends on the energy needs. If your DMS is well designed and has energy efficient LEDs and components, then you can have enough light output with less energy and you can use a reasonnable and affordable solar system. SESA SolarSign are as visible as the power grid DMS and matches NEMA TS4 optical requirements.
4- Solar Powered DMS can be mounted on overhead structure - TRUE
Absolutely! An energy efficient solar powered DMS can be mounted overhead, on a cantilever, road side high masts, or poles. The power used by equipement mounted inside the DMS housings is either 24V or 48V DC. It is not a problem to bring power to an overhead sign from a solar system installed on the ground. It is a matter of distances and power cable sizes. Again, energy efficiency is important. If you do not need that much power, the cable gauge will be smaller and the distance between the DMS and the solar system longer.
5- Solar Systems Require Too Much Maintenance - WRONG
Solar panels basically do not need any maintenance at all. It may be advisable to wash them from time to time if the rain is not enough in order to get rid of dust and dirt. Most of the time, it is not necessary.
Most recent batteries do not need maintenance, they are no longer lead acid but most of the time gel batteries. If they are correctly sized, they will never be discharged so there is no need for replacement.
The other equipment of a solar system like solar chargers do not require more maintenance than other DMS equipment. They are most of the time connected to the control center and management software the same way the sign is. If there are faults, the system will automatically be alerted and troubleshooting team can be dispatched to the site.
6. Solar Powered DMS are Too Expensive - WRONG
The Initial costs may be higher than power grid DMS, but when you take into account installation costs and energy costs, the Return On investment is only 4 to 5 years depending on DMS size and location. With a solar powered sign, you don't need to get energy from the grid, pull miles of cables, install power feeders and other electrical devices. And because power is locally generated, you do need to pay electrical bills whatsoever.
7. The Technology of Solar Powered Dynamic Message Signs are a Too New and Has Not Proven Reliability Yet - WRONG
Solar technology keeps on improving! We have been seeing portable DMS on the side of our roads for many years. The technology has existed for a very long time and has proven reliability and efficiency. We are now bringing solar technology to the overhead DMS on large highways and remote places. With the newest generation of solar panels, they are 50% more efficient than the first generation. Batteries also have better resistance to higher temperature ranges and can produce more energy.
What Did we Learn?
Well, there are few things to remember. Energy efficiency of the new dynamic message sign generation and accurate solar system calculation allows solar power dynamic message signs to be deployed anywhere and to be installed in many ways including over the highways. Maintenance and operation costs are reduced and the return on investment is pretty fast. In other words, the industry is ready to deploy solar power dynamic message signs for the benefits of the tax payers and the environment.