Sizing an Off-Grid (Battery) System

Sizing an Off-Grid (Battery) System

If you have decided to use an off grid system instead of a grid-tie system (either the grid is unavailable, or not cost effective to connect to), then keep the following few items in mind:

First, you will need to be VERY accurate on your energy consumption analysis. If you under estimate your power needs, you are going to sitting in the dark for a while. Make sure that when you list all the items in your home (and their power consumption) that you are realistic about how often you use these items and for how long. Often times people will estimate based on a ‘goal’ of energy conservation they hope to live up to in order to save some money up front. It is best to be honest with yourself from the beginning.

That being said, if you can make some changes in your lifestyle and make some energy conserving modifications to your home you WILL save a lot of money. It is estimated that a person can save approximately $5.00 on up front investment for every $1.00 they spend on conservation (solar water heaters, LED light bulbs, insulation upgrades, etc.).

Second, try not to over estimate. While you may be better off to have too much power rather than too little, it will affect your cost. If you over estimate your project, it may become cost prohibitive unnecessarily and the extra power is simply ‘lost’. You are not able to sell the excess to the utility company like you can with a grid-tie system.

Third, an off-grid system will require a larger investment due to the need for batteries. The batteries will also add to your maintenance costs. We will discuss different types of battery banks in future posts.

For most people the choice to go with an off-grid system for a home is purely because there is no other alternative. Other applications include a small system for an RV or a remote garage or workshop.

As always, I encourage questions and comments.

Paul Juell

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October 21, 2012 at 6:38 pm 1 comment

Off-grid Systems vs. Grid-tie Systems

Off-grid Systems vs. Grid-tie Systems

Are you trying to decide between installing an off-grid system or a grid tied system?

The first consideration (and often times, most important) is cost. In most cases, the only reason you would do an off-grid system is because there is no practical way to connect to the grid.

By being ‘tied’ to the grid you have a built-in back up plan for times of high usage as well as a way to sell the excess energy you produce during other times. This set up gives you the least expensive way to plan your system based on average use.

Installing an off-grid system involves a little more planning since you do not have the advantage of a back-up. It will also cost you considerably more money because you have to make allowance for a battery bank. In addition to the up front costs of a battery bank, you will also run into future costs related to maintenance and replacement of the batteries.

Overall, when possible it is preferable and more cost effective to connect to the grid when it is available. Possible exceptions include smaller projects like providing power to a remote garage or workshop.

This is not to say that off-grid projects are impractical. There are definite situations where they make perfect sense. As with any solar or alternative energy project your most valuable investments will be in planning, education, and when necessary-professional advice.

Paul Juell

September 14, 2012 at 7:25 pm Leave a comment

Do-it-Yourself Solar – Is It Feasible?

Do-it-Yourself Solar – Is It Feasible?

Here’s a common question: “Can I install solar myself?”

The answer is a definite maybe! Actually, that is always a very hard question to answer because there are so many variables. The two main questions to answer up front are; what are your goals for your project, and what level is your personal skill set?

Different goals for your solar project will dictate the complexity level of your project, not just in terms of installation but also in terms of permits and required inspections for your area. A battery (off-grid) system for example, will require more effort in the planning stages than a grid-tie system.

As far as your skill set goes, it is important that you are realistic and honest about what portions of the installation you are and are not comfortable with. Even if you are completely qualified to do all the work involved, your municipality and/or utility will require some of the work to be done by a licensed professional (usually the final wiring – especially when connecting to the grid).

In any case, the main reason this question comes up is because consumers are interested in keeping the cost down. Whether you are getting off the grid partially or completely, and whether you are doing it to save money, be environmentally friendly, or both, going solar can be expensive. The more money you can save up front the closer you can get to your overall goals.

What I recommend is a little of both. Purchase the components you need and the qualified labor separately. By doing your homework up front and handling the sizing and planning on your own, (and maybe even some of the installation) you can literally save thousands of dollars!

You can do a lot of the ‘leg-work’ and not only save money, but also have a lot of fun doing it. In addition to the ‘fun’ value, you will also have a huge sense of satisfaction as well as a working knowledge of the components and process that make up your system. This knowledge can be very valuable if you need to perform maintenance or if you plan to expand your system in the future.

All these aspects will be covered in more detail in future posts. Any questions? Contact me.

Paul Juell

August 30, 2012 at 4:39 pm Leave a comment

Another Quick Way to Size Your Solar System

Another Quick Way to Size Your Solar System

A few weeks ago we discussed how to size your solar system based on your energy use. This time around, I would like to discuss how you can do it based on your roof size.

This method is best used if you don’t really have enough available space to do as large a system as you need (or may want). Even if you are not able to generate 100% of your home’s electrical needs (which is a pretty tough goal to meet even in the best case scenario), it makes sense to do what you can.

  1. Find an area of your home where the roof faces South, or as close to South as possible. Make sure there are no obstructions such as trees that may shade your panels. Tip: look for trees that may grow in the near future and become a problem. Tip 2: Remember that the sun is much lower in the sky in winter!
    1. For our example, let’s say the roof area is 20 x 30 feet.
  2. Subtract 3 feet from the top ridge and from each side (not the bottom on a pitched roof).
    1. This equals 17 x 24 feet or 408 sq.ft.
  3. Divide by the size of the panel (+/- 16 sq.ft.).
    1. 408 divided by 16 = +/- 25 panels
  4. Multiply by the panel watts (+/- 230 depending on the panel)
    1. 25 x 230 = 5,750
  5. Divide by 1,000.
    1. 5,750 / 1,000 = 5.7. You have enough room to install up to a 5.7 kW system.

If this gives you enough power, than great! If not, that’s okay too, do what you can! I hope this helps you out.

A couple things we will be discussing soon; your system does not need to face due South (but it helps), and the angle you set you panels matters!

Please follow me on Facebook for more information.

Paul Juell

August 13, 2012 at 11:49 pm Leave a comment

Solar Panels vs. Blackouts

Solar Panels vs. Blackouts

 “Will I loose power in my home during a blackout if I have solar panels”?

The answer is maybe. The type of solar (or wind) system you have will determine that. There are different ways to set up your personal solar system and they will react differently.

When people think of solar systems they often think of being totally off-grid and independent of utility companies. While this is a very achievable goal, in most cases it isn’t always cost effective.

There are many ways to set up your system and for now we will discuss the two most common; grid-tied and off grid.

With an off grid system your power generation (solar panels, wind turbine, etc.) system will run through a ‘controller’. This controller regulates the power flow for two main reasons; to keep your batteries from overcharging (and getting ruined), and to keep them from discharging completely (and greatly shortening their life span).

From there your batteries get charged and you are ready to power whatever appliances, lights, etc. that your system was designed for. Of course, there is much more to it than that, but for our discussion today let’s leave it at that.

By definition, you are now off grid and power outages will not affect you.

With a grid-tied system your power generation in tied to the grid. There are huge advantages to this type of system:

  1. You do not have to have as large (and expensive) an array since you have the grid to fall back on during periods of higher use/lower production.
  2. You don’t have to change your lifestyle to account for energy usage.
  3. You can sell (in most cases) your excess power to the utility company.

But here is the downside. You will loose power during blackouts! You may wonder why that is – if the power outage happens during the day (or when it’s windy in the case of a wind turbine) it would make sense that you are still producing energy.

Well, in reality that is the problem. You are tied to the grid. Your grid-tied system will sense a power outage and your inverter will cut your power production. The reason for this is because a solar system can generate huge amounts of power and it would be unsafe for your system to feed power into the grid while technicians from the utility company are attempting to make repairs.

You can design a system that will run as a backup during power outages, commonly called grid failover systems. We will discuss those types of systems in future posts.

If you like the type of information you see in my posts, you can find much more on my Facebook page. Please take a moment to ‘like’ my page here: http://www.facebook.com/pages/Go-Green-Tucson/442222549132094?ref=hl

Paul Juell

August 5, 2012 at 7:50 pm Leave a comment

Return on Investment – Is Solar/Alternative Energy cost effective?

Return on Investment – Is Solar/Alternative Energy cost effective?

This is a question I get everyday; “When will I recoup my investment?”

Let me start by first saying that there are more ways to measure benefit than just dollars and cents. Many of us feel a genuine sense of accomplishment and pride by doing something that is very positive for the environment. There is a value to that!

There is a value to having the knowledge that we are not completely subservient to outside influences such as utility costs that we have no control over.

I hear people tell me everyday that the United States should reduce or eliminate her dependency on foreign oil. I agree with that statement, but at the same time that big of a change will start with each of us – at home. We, as individual families, can achieve ‘personal energy independence’ today. The technology is there and is getting better and more affordable everyday. Personally, I don’t want to be dependant on anybody if I don’t have to be.

Okay, I’m getting off my soapbox now. Let’s talk about ROI (return on investment). Let’s talk about it in dollars and cents. And if you are concerned only with dollars and cents than this should make sense to you. And I don’t want to hear any comments about ‘debt’ either. First of all, you are in debt to the utility company whether you want to admit it or not, and this is a debt you will never pay off (unless you buy a tent and live off the land).

Secondly, if you want to talk only in terms of money, than this is a practical argument not an emotional one, and fear of debt or obligation is emotional.

Let’s approach this with a very simple example (and these are typical numbers that I work with everyday). A homeowner wants to make some energy saving/producing improvements in his/her home. Here is how the numbers often work out:

 Current utility costs (monthly average): $250.00

Cost of improvements: $12,500.00

Projected monthly savings (average 35%): $87.50

The goal here is to pay the cost of $12,500.00 with $87.50 per month or less. That would be the break even point. Okay, here is how it works:

The Federal tax credit will give us 30% (dollar for dollar) <$3,750.00>

In my location the state tax credit is 25% (up to $1,000.00) <$1,000.00>

In my location, the utility companies will give (approximately) <$1,250.00>

With theses rebates and incentives that total $6,000.00 the amount now coming out of the homeowner’s pocket is ONLY $6,500.00! So in order to break even, and therefore see a return on investment, we need to pay $6,500.00 off with $87.50 per month.

Okay, let’s do the math…

A 10 year loan for $6,500.00

Interest rate of 5%

Payment equals $68.94

Monthly savings equals $18.56

The homeowner is already seeing a positive ROI. Okay some will say that if you finance it you will be paying more in interest. Yes, but as long as the positive cash flow (savings) is paying the principal AND interest, cash flow IS positive and ROI is realized! In this example the homeowner could pay up to 10.44% interest and still break even and therefore reach ROI.

Also, keep in mind that a loan payment will, in most cases, remain the same, while the amount saved will go up with the energy rates. If you don’t believe that utility rates go up, find a bill from just a couple years ago and see for yourself.

Of course every situation is different but I hope this helps. As always, I look forward to your comments.

Paul Juell

July 30, 2012 at 8:26 pm Leave a comment

Useful Equations For Measuring Electricity

Useful Equations For Measuring Electricity

Wow! That sounds exciting, right? lol

I know this isn’t the most sexy topic but a basic understanding of how things work will make the sexy stuff make more sense. Each of the different terms we discussed in my last blog have a relationship to each other. This relationship is useful to understand (at least at a basic level). I am certainly not an electrician and I don’t plan to become one, so bear in mind this is just a basic overview that may help things more clear to you in the future.

V = Volts (The measurement between two points – ex. the positive and negative tip of a battery).

I = Amps (This is a measure of the electrical current – the flow of electrons within a wire or a cable).

R = Ohms (A wire or a cable has inherent resistance within it, this is how it is measured).

W = Watts (Watts are how we measure the power of electricity. The higher the wattage, the more power an appliance requires).

P = Power (Measured in Watts).

E = Energy (Energy is measured in joules. One watt-second is equal to one joule. Energy is power multiplied by time and is in most cases expressed in watts. Ex. watt-hours [Wh] or kilowatt-hours [kWh]. 1,000 watt-hours equals one kWh.

Voltage is equal to Current X Resistance. ( I x R = V ) Like any equation, if you know two of the three variables you can find the third. Here are some examples: Volts divided by Resistance equals Current ( V / R = I ) Volts divided by Current = Resistance ( V / I = R )

Power is measured in watts, it is expressed as volts times current. ( V x I = P ) Here is a simple example to help illustrate this equation (From the book Solar Electricity Handbook 2012 Edition by Michael Boxwell (This is an excellent book for someone just learning about solar power):

A 12 volt circuit with a 4 amp current = 48 Watts (12 x 4 = 48) Like before, if we know the other two variables, we can work out the volts.

Power / Current = Volts ( P / I = V ) A 48 watt motor with a 4 amp current is running at 12 volts. (48 Watts / 4 Amps = 12 Volts)

Current = Power / Volts ( I = P / V ) A 48 watt motor with a 12 volt supply requires a 4 amp current. (48 watts / 12 volts = 4 amps).

I hope this brief explanation at least demonstrates that there is a relationship between these measurements of electricity (and that you are still awake). As I stated earlier, this may not be the most exciting information but it is critical that you have a basic understanding before you begin planning your system.

Paul Juell

July 26, 2012 at 10:26 pm Leave a comment

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