Grid Tied vs. Off the Grid Solar Systems

February 7th, 2010 by admin | No Comments | Filed in Solar Equipment

What is the best option?

Here is another decision that is usually answered rather quickly and early on in the solar decision making tree.  First of all, there is a major distinction that needs to be clear about PV solar systems.  One option is to install a “Grid Tied” system.  That means, the solar system will be connected to your utility company’s nework(the elctric panel).  The other option is to be “Off the Grid” which would mean the system does not connect to your electric panel(imagine you live where there is no electric company, i.e you don’t have an electric bill)  There are quite a few variations, but that is the general idea.

Why would you want a Grid Tied System?

People chose grid tied systems for many reasons.  Here are a few: cost, net-metering, incentives, less maintenance, more installers know how to install them.

Cost

Grid Tied systems have the following costs:  panels, inverters, disconnects switches, wiring, mounting hardware, labor to install, permits if necessary(usually a nominal fee, nothing too big)

Net-Metering

The net metering option allows a “grid tied” system to connect to the grid and put excess unused electricity back into the grid, otherwise it would be wasted.  This is a benefit because the owner of the system can effectively “sell back” their electricity if they don’t use it.  This doesn’t mean the electric company will be writing you a check everyday, but they very well may give you a credit on your electric bill if you have given them more electricity than you have used for a particular month.

Incentives

In some states and areas, solar incentives are only eligible for “grid tied” systems.  That is something you will want to check with your local solar professional.

Maintenance

Grid tied systems are by and large, much easier to maintain.  When installed correctly, they can run on their own for an indefinite amount of time.  If you are having to tweak and mess with a grid tied system after it has been installed, than the installation was not done correctly.  These are no hassel systems after they have been implemented which is one of the major reasons grid tied systems are so popular worldwide.

Why Would you want an Off Grid System

People tend to chose off grid systems because they are not near utility power, the utility company is not reliable(3rd world countries), want a sense of energy independence, want a backup supply of electricity if the power goes down, and many more.

Utility Power is Far Away

If the local utility lines are so far away that it is too expensive to pay for new lines, an off grid system might be a good match for you.

Not Reliable Utility Company

Some people on the planet have such horrible times actually receiving electricity from their local or government utility company that it simply is not an option to rely on that, this makes off grid solar a good option.

Energy Independance

If you really put a value on supplying your own energy all of the time, and want to tell the utility company to disconnect your lines, off grid solar could be perfect for you.  That is what it allows you to do.

Backup Power

There is an “off grid” but still “on grid” hybrid way to this too.  If you wan to be connected to the utility company, like the “on grid model” but still want to have a gauranteed source of power if the utility power ever goes out like from a hurricane.  You can create a hybrid solar system.  This would actually connect to the grid, but would have batteries which would store power too.  This way, if the power went off, you would still have electricity in your batteries to use., and the sun to generate more power over the coming days.

Tags: , , , ,

How Many Solar Panels Can Fit on My Roof?

February 1st, 2010 by admin | No Comments | Filed in Solar Equipment

Here is another question that everyone wants to know.  How many panels can get up there.

Of course the answer is different for each home.  But, it is relatively easy to get a good idea by doing some simple math that anyone can do on their own.  The average solar which is either 175 watts, or 200 watt panels is about 5ft by 3ft.  So that is about 15 sq. feet per solar panel.  These actual numbers are a tiny bit larger than the most common sizes, but they work well for rough measurement purposes.

If you have a roof that faces the south(which is great for getting solar radiation in the northern hemisphere) and that roof has dimensions of 30ft x 20 feet, we can get an answer.  If the 30 ft is the width, and the 20 feet is the height side(meaning the 20 foot side rises to the top of your roof) then you could easily get 3 different rows of solar panels on that roof. Look at the diagram below which will represent the roof

<-30 feet this way for the roof->

X X X X X X X X

X X X X X X X X      } 20 feet up and down this side for the roof

X X X X X X X X

So if each X is a solar panel, there is more than enough room for 24 panels.   This would even leave 2 1/2 feet of space on the top and bottom, and 3 feet of space on the sides.  It is best to have some space around the outside of the panels to work with, also many local building codes require space around the solar panels for the fire department to have for walking space in the event that a fire does happen.  ***Most important, make sure to check if there are any non standard building codes in your area.  A local solar professional should be able to help you out with this type of question.  But, be wary if someone tells you that you should put panels all over the roof, and completely cover it, that is not a good idea.

Tags: , , , , ,

How Much Solar Energy Do I Need?

January 20th, 2010 by admin | No Comments | Filed in Saving Money with Solar

Everyone asks this question at some point.

How much solar is needed? Most of the time, this question is asked from a homeowner to a solar professional.  The answers of course vary.  What is usually assumed is the homeowner is asking about how much solar is needed in order to take care of all the electricity needs of the house.  Already there are all kinds of assumptions going on in the head of the homeowner.  But lets look at this question, “How much solar do I need?”

The answers are unique to every house, and there are several variables involved(location on the planet, shade from trees which would limit solar production, heat factors, snow factors, roof angles, or ground angles towards the sun, and then there is a very complicated variable of the local state incentives for solar power.

Let us start by doing an example of a house in San Francisco, California.  According to data from the department of energy, San Francisco receives 5.2 hours of sunlight on average per day per year.(What the heck does this mean?)  Well this means that if you took all the days in the year(the long summer days, and shorter winter days) and added up all the hours of sunlight, and then divided by 365, you would be left with a number.  The number is going to be more than 5.2, but all sunlight hours are not created equal.  This means that when it is 8:00am the solar panels do not produce as much electricity as they do compared to lets say the middle of the day.  Either way we need to come up with a number that equals the average number of sunlight hours per day per year that can create maximum output on the solar panels, and that number is 5.2.  Please realize, you want this number to be as high as possible.  For example, in some parts of Arizona this number can be over 7 hours per day, which is dramatically different than lets say 5.2 sunlight hours per day.

Shade from trees is not good for making solar energy if the shade hits the solar panels.  That is a basic concept, so lets not freak out about that too much.  Some people go ahead and cut down some parts of trees in order to maximize the solar panels production.

Heat is a factor, but for much of the US, it is relatively small compared to factors that can reduce energy production.  The bottomline is worry about shading from trees before you worry about the solar panels being too hot or cold.

The angle of the solar panels towards the sun is a very important variable.  For the most part, the best angle for generating the most electricity throughout the year is this equation: Your location’s lattitude minus 15 degrees.  For the San Francisco Bay Area, that comes out to about 22 degrees give or take.  So solar panels around here should be mounted towards the sun at about 22 degrees.  That will make the most energy.  Yes of course, if you have panels that rotate during the day, they surely will make more electricity, but that type of setup is very costly and most homeowners don’t go that route, so lets not get into that too much.

In general, you want to point your solar panels to the south at the angle we talked about in the paragraph above.  Since we are north of the equator, that is why we have the panels face south, it would be different if we lived down in Argentina.

So lets do a little math.

Look at your utility bill.  You should see the number of kilo watt hours of electricity you used for that particular month.  That is the number we need to know. Say for EXAMPLE you used 900 kwh for that particular month.  That would come out to 30 kwh/day since there are about 30 days in the month.  That would mean, your solar system would need to produce 30 kwh in AC to power your home, and keep up with your needs ON AVERGE.  So, the next logical question is, what does that mean in terms of a solar system size?

Here is the answer:

30 kwh per day means that in the exmple of San Francisco, where we have 5.2 sun hours per day on average, we need to make about 5.8 kwh for each of those sun hours.

Since Solar systems are not 100% efficient, some energy is lost in the process which can’t be avoided.  So, we need to find out how many solar panels are needed to do that for us. Lets assume that 20% of whatever is produced on the panels is lost in transmission.  So, the 5.8 kwh really needs to be 7.25 kwh produced at the panels which after losing 20% will really become 5.8 kwh.

That means that we need a 7.2 kw solar system.  From a post from a previous solar installer on this blog, he said systems are running about $6/ watt.  A 7.2 kw system is equal to 7200 watts.  So $6 x 7200= $43,200

WOW that’s a big number.  Now we need to look at the incentives, since the average price of electricity in the country is about $0.12/kwh.  That means that this system producing 900 kwh/month is saving: $108.00

That is not a great looking financial equation right now.  So we need some help, and there are incentives for that.  Take for example, the 30% federal tax credit.  That is a big number.  Then there are all types of local incentives, many times from the local utility company, and other times there are solar incentives on the city level.  Also, look for state level incentives.  In California for example, this type of system would be eligible fo rabout $10,000 in state level rebates.  Not bad, and definitely changes the financial equation.

Please post your comments, I will try to answer them all.

Tags: , , , , ,

Tips and ideas to consider for implementing a solar system

January 14th, 2010 by admin | No Comments | Filed in Saving Money with Solar

Hi Solar People,

If you have a good deal of experience with home PV solar systems, please post some big ideas that you think every homeowner should consider and think about with regards to a solar project.

Thanks,

Adam

Tags: , ,

What is your opinion on the best solar panels?

January 10th, 2010 by admin | No Comments | Filed in Solar Equipment

This is one of those subjects that we could talk about for days, months, years.  Every salesperson from every solar company always says they know everything about all the solar panels, and the one’s they are promoting are the best.  I simply don’t buy it.  What seems to be the reality most of the time, is solar panels are basically very very similar in terms of the output they give in kilo watt hours.

Of course solar panels have all different types of dimensions, colors, warranties, this and thats… but lets face it, we would need 7 or eight people’s fingers to count the number of solar panel manufacturers over in China who are making nearly all of the panels.

From my experience, people who are wanting to put solar panels on their house are very concerned with “which panels” are the best.  And most of the time, I would say a salesperson is going to tell you theirs and rattle off a long laundry list of reasons why.  But in the end, the next salesman is going to do the same talk with the panels that their company happens to purchase from their distributor.

My advice would be this, figure out which panels have a good warranty, ask the local installer about some references(VERY IMPORTANT), and then decide which panels match your personal taste as far as looks.  The output is going to be very very close to nearly all other panels.  In fact, some panels have names of two different companies when in fact they are made in the exact same building over there in good old China.  Funny how that happens.

I am hoping this will spark some great comments, since this is a question that everyone asks when putting on solar panels.  Come on, there was no “Which Solar Panels are the Best for your Home or Business” class in high school was there?

Tags: , , , , , , ,

Solar is a longterm plan right?

January 10th, 2010 by admin | 3 Comments | Filed in Saving Money with Solar

Is Solar the Right Thing to Do, quick answer is yes.

But, this is a rather loaded question.

After being involved in the residential solar energy field for quite some time now, I thought it would be beneficial for me to put together some information for the typical homeowner who is considering going solar.

There are many different things to think about before getting a solar professional involved ( they are sometimes referred to as “installers”).

Here is the first question everyone should ask themselves: why am I looking into solar right now, what are my reasons for wanting solar power?

Once you have asked yourself that, and come up with some answers that are true answers, you can begin to find out if solar is a good idea for you.

Let us get right to the point,
in the hundreds of interested homeowners I have talked to over the year, everyone wants to know what the investment in solar looks like. Before breaking into other points about solar, let us address the costs and returns you can expect from a solar system.

Please realize that if you are the type of person who is currently having a hard time paying your electric bills, car payments, mortgage etc… solar is probably not going to be possible until you have some more disposable cash. Systems usually run between $20,000-$40,000 prior to any incentives. After incentives, the systems can cost quite a bit less, but you are still going to need to find many a thousand of dollars.

If you are still with us here, let me tell you some of the bright points of solar. It lasts a very very long time, systems should be on your roof working well for over 25 years. That is one of the most important things to realize, they will be with you longer than most of your neighbors!

What Size Solar System is right for you? It depends on what percentage of your electric bill you want to have covered by solar.
Also, it depends on how much available space you have, you may want to cover all your electricity with solar, but if you only have enough space to cover half, then there you are… For the purpose of getting you on your way to understanding a solar system’s size, I will assume that you have good access to the southern skies, and no shading from trees or other buildings.
Here is the math:
take the total number of kilo watt hours you purchased from the utility company the past twelve months. That number will be your kwh annual total. Next take that number and divide it by 12 to get your monthly average.

Next, take that number and divide it by 30 to get your daily average.
So this number is the number of kwh’s that the solar system would need to produce on average per day per year to meet your 100% needs.
At this point to figure out exactly the size system you need, we would need to know your location on the planet, as that will dictate how many sunlight hours you receive on average per day per year. This number is between 3.5 to 7 depending on where you are in the country. These hours are hours that the solar panels can operate at optimal efficiency, you may think you have 15 hours of sunlight some days of the year, and you do, but all sunlight hours are not created equal. For example, when the sun is coming up in the morning, it does not operate the panels at 100% efficiency. Take weather changes, clouds, and seasonal differences, and you will be between 3.5-7.

Back to the math,
to get the system size you need, take your daily total kwh use and divide by average daily sunlight hours. That will end up being the output the Solar System will need to have per hour in AC (Alternating Current) per hour to meet your 100% electric needs. Since Solar Systems are in DC (Direct Current) you should multiply the number you just got by 1.2 to bring your system size to a DC number. This is the system size you would need to meet your electric needs. What would something like that cost? Well, right now, the national average for residential Solar System installations (grid tied PV systems) is just about $7.00 per watt prior to incentives. That would mean that if you came up with a number of 6 from the math above, that would equal 6000 watts, and when multiplied by $7/watt you are at about $42,000 for that size system after shipping and installation.

Because the initial investment in Solar Power Systems can be expensive, it is feasible to think about the ways in which the costs can be reduced. If a person is technically oriented or very good at home improvement, it is possible that they might consider building their own solar system. The amount of electricity or heat that can be generated is directly influenced by the wattage of the solar panels, as well as by the intensity of the sun light that touches their surface. First, of course, it would be important to learn how solar panels work, what materials are required, the cost of the raw materials and the availability of them, and finally the difficulty involved in assembling and installing them. In the long run, will your effort be rewarded with a solar system that will serve you for a reasonable period of time?

Tags: , , , , , , , , ,