RTA bus shelters ACs by Solar – Not a good idea

Dear All,

It was recently reported in the local news paper that the local transport agency of Dubai (RTA) is considering using solar energy for running air conditioners within the bus shelters.  Here is the reason why I think it is not a good idea

1. Economics: The average size of each air-conditioner is about 5KW.  Let us say that it is going to run for 12 hrs/day; so the total energy required per day is 60KWhr.  To have solar power (off grid – it seems like this is what they are referring to in the article), the initial set up cost adds up to about $150,000.00 (conservatively).  Compare this to the prevailing cost of electricity in Dubai of $0.07 per KWhr.  Savings per day is 12 x 5 x 0.07 = $4.20.  Breakeven point for the initial investment is $150,000 / $4.2 = 35,700 days or 97 years!  Anybody needs a calculator?

2.  Feasibility: In order to deploy a system of this kind, you would need installation of about 14KWp.   Total area required for installing a system of this size, you are looking at 140m2.  Assuming typical width of footpath next to the shelter where the installation is done to be of 5m, it’ll need 70 meter (unobstructed) footpath for doing the installation.  This is close to a typical city block! Unless, RTA plans to elevate and provide shading to the pedestrians using PV modules, no reasonable solution is possible to put these modules.  Add to this complexity in finding unobstructed locations for mounting PV modules within the city with high rise buildings.

Here is what is possible, however.

It is known that a direct air ventilation creates a feeling of temperature about 20 degrees lower than ambient.  If fans could be mounted inside the shelter along with vents (all DC rated highly efficient motors), then you could essentially provide relief to the passengers from scorching heat outside.  PV modules should only be used in places where grid supply is not available.  The shelter roof could be used for mounting PV modules for this load.Can solar power be used for these shelters?

Myth behind Solar Street Lights

Hello visitors and bloggers!

This is the first official blog of Apex Power Concepts!  You are welcome to leave a comment(s) and share your opinion about the topic being discussed.

The first article is about Solar Street Lights – more specifically the myth that surrounds solar street lights!

Solar street lights essentially street lights powered by batteries that get charged by solar PV modules (sun energy to electricity).  All the components within the system are mounted on a single pole.  The main components within the system include PV modules, batteries, charge controllers and switchgear.

Now, to the myth.  According to some proponents of solar street lighting systems, all the solar street lighting systems are a. good way to save money and b. environmentally green solutions.

Here is why both the above claims are plain flat false.  Let us start with the first claim that solar street lighting system is viable.   Lets take an example of a typical installation that requires solar street lighting system for 10Km of road.   Typical installation involves using 120W LED lamp on 10m pole, with pole to pole distance of 40m.  With this arrangement, we are looking at total 250 street lights. This assures a good consistent light spread of about 15 Lux.

If normal AC lamps powered by grid are used, the extra cost involves cabling and other related civil works (cost about $300,000) and annual cost of running the lamps ($9,000 per year or $36 per year- $0.07 per KWhr – current rate of electricity in the UAE).   Typical installed cost of each pole – $1,250.00.  Therefore, total costs  per lamp adds up to $2,550 + $36 per annum.

Now, let us look at solar powered street lights.  The installed cost of each lamp falls around $2,000.00 (very conservatively).  Now, let us add maintenance (cleaning of modules) at $200 per pole per year, changing batteries every 3 years @ $500 which is essentially $133 per year.  Therefore, total cost of solar street lights is $2,000 + $333 per year.

You don’t need excel spreadsheet to comprehend the different in cost of ownership.

Moving on to the second part of the myth that solar street lights are good way to save the environment.  Here I call you attention to the following link


USA, that promotes recycling through programs like free collection of bad batteries at various collection points spread across the country, gets the collection of old batteries as been at dismally low level of 10%!

What happens to the balance of batteries?

Again, may I bring your attention to the following page


I quote from the above link

Some lead compounds are extremely toxic. Long-term exposure to even tiny amounts of these compounds can cause brain and kidney damage, hearing impairment, and learning problems in children

And more..

While lead recycling is a well-established industry, more than 40,000 metric tons (39,000 long tons; 44,000 short tons) ends up in landfills every year. According to the federal Toxic Release Inventory, another 70,000 metric tons (69,000 long tons; 77,000 short tons) are released in the lead mining and manufacturing process

I don’t see any green part here!  90% of the batteries typically end up in the most destructive way into landfills.