Photo voltaic Estimator

[Npstewart]

Anyone know a good resource to estimate the savings associated with installing solar panels on a commercial office building. The building would be new construction. The only thing I really know is the square footage and roof area. Obviously I know it would only be an estimate. Thanks Everyone!!!

 

[K8MHZ]

Anyone know a good resource to estimate the savings associated with installing solar panels on a commercial office building. The building would be new construction. The only thing I really know is the square footage and roof area. Obviously I know it would only be an estimate. Thanks Everyone!!!

All I can recommend is what I did, and that was to take a college class on it. 'Savings' estimates are quite complex and I wouldn't recommend trying it alone on the first run. Hire someone to do it. Besides square footage, you also need to know what the shading is like and how it will affect the overall output of the array. To do this you need a device such as a Solar Pathfinder along with the knowledge of how to apply the patterns from the Pathfinder to the math for the output figure.

I put 'savings' in apostrophes because at today's price per output, there will be, unfortunately, no savings realized for 20 to 40 years. What is normally provided for the customer is an ROI or return of investment. That is the date in which the output of the system has paid for itself and from that date forth supplies 'free' power.

There are also legal and utility aspects to consider if you want to do net metering.

 

[Npstewart]

Ok, how about the KW generation per square ft of solar panel (average).

 

[K8MHZ]

Ok, how about the KW generation per square ft of solar panel (average).

The popular panels are about 3 x 5 feet and put out 240 watts.

We consider average insolation to be about 1000 watts per square meter at 100 percent. The efficiency of the panel times that figure will give you watts per square meter.

So, with today's panels, figure 16 watts per square foot. (Yes, they are that inefficient)

 

[97catintenn]

You can start with the average solar watt hours per day for the location. For me in TN, that would be 4.5wh per day.

On a simple plan, if I had a 200w array on a yearly average, it would produce (200w*4.5wh) 900watts per day at the panel. Then I would take into account eff of the panel, eff of the inverter, and power loss in the conductors from the panel to inverter.

Inverter eff 80%
Panel eff 80%
I'm down to 576watts per day. And then I would calculate the power loss from the conductors to the inverter. But let's skip that step for this example.

576w 365 days per year = 210.24kw

Here in TN I pay about 11cents per kw. So 210.24kw @ 11cents = $21.03

For the year, I would recoup $21.03 per year on my investment, assuming no maintenance or upgrades.

 

[Npstewart]

I appreciate the input from both of you, I have a good starting point now. I guess I wasn't aware of the dynamics of the this.


I know it usually takes decades to recoup any money from these type of systems. I wonder what happens if these things get damaged by hail, birds, tornadoes or hurricanes. If you had these things covered with insurance, the premiums would have to be extremely high which would eat away at your savings.


It would be nice if we could see a break though in this technology to make them affordable.

 

[K8MHZ]

I appreciate the input from both of you, I have a good starting point now. I guess I wasn't aware of the dynamics of the this.


I know it usually takes decades to recoup any money from these type of systems. I wonder what happens if these things get damaged by hail, birds, tornadoes or hurricanes. If you had these things covered with insurance, the premiums would have to be extremely high which would eat away at your savings.


It would be nice if we could see a break though in this technology to make them affordable.

We used the Sanyos at school and I don't think hail or a bird would hurt one. You could easily stand on them. They ran about 600 bucks per panel and were very well built.