24VDC system in the making!

      Hello! So it seems that I will in fact be able to move forward with my 24VDC system in the very near future after all! Of course as things would be I have to make some changes to how I will proceed but the fact is... I will very soon be building my new system!!! And yes, I will post with images the new system as it goes up and comes on line.

      This particular post I will be focusing on a new spreadsheet I have set up that I would love to share with you that are reading. The idea was to create a way to track costs and really compare components by cost, feature and need. The spreadsheet (which I will link to at the bottom of this post) is essentially a live one that I am using to build my upcoming 24VDC system. I have a limited budget (yeah... really who doesn't today!) so I need to put a lot of thought into the items I purchase and where my money goes.

      In an earlier blog post I mentioned converting my AC refrigerator and freezer to DC, and this is still going to happen, just not for a while. The conversion cost is pretty high and while the payback is reasonable I just don't have the money at the moment to do it. So I will be using an inverter to run the refrigerator for now. Now currently I expect the refrigerator to consume about 90AMPS of power per day. BUT I have a plan to reduce that!

      See the idea is to improve the efficiency with as little cost / effort as possible. And the only real way I can do this is to improve the insulation of the current equipment. And since I will have to do this anyhow for the DC conversion, well I will be just one step ahead! So the wife and I will add hard foam insulation to the exterior of the fridge (See here) then she will put a nice finish exterior over that. I will admit right here and now my wife is better than I am with finish carpentry so I do the rough stuff and she does the finish. By adding the extra insulation and installing it in such a way that is seals around the gasket area, we will increase the efficiency of the chill box and reduce the run times of the compressor. This should net us an estimated 30-40% decrease in power consumption.

      And if it works as I think it will (it's all theory right now) then I can do the same thing for my deep freezer that I have. And that would be the bomb diggity right there! So that is really the major change I have in my current plans.

      Now the planning spreadsheet that I have put together is pretty simple to use really. And all you have to do is download it and tweak it for your needs. I was going to use Google docs again but it's a pain in the ass to take the spreadsheet and recreate it there so I am using a free file sharing site for now. Anyhow to use it is simple, the areas that are light gray and have a border around it are where you make your manual entries. The top portion is called the component pricing list. Here you enter the component(s), their unit cost (how much each item costs) the tax rate if applicable and the shipping rate. Keep in mind this is not accurate and is essentially and estimation form. The whole idea is to allow you to see how much your components will cost and plan accordingly.

      It also again will touch on your load requirements and will you meet them with the items you are selecting. Anyhow the next area in the components list is the source and URL, where are you planning on getting this stuff. As you enter items the F, G and H fields will auto-calculate for you. Then in column|row H12 a total sum will be auto-calculated. In column|row H13 you enter the amount you have budgeted and below that the estimated remainder will be auto-calculated for you.

      Now you will notice that in column|row I14 there is an area that is gray and had borders, this is where you put the actual remaining amount. What I mean by that is I will often times start the purchase process so I can see exactly how much shipping and tax will be and get a total value. I will then take that total and put it somewhere and add other actual totals to it. I don't commit the purchase (not until I am finished shopping and I have the $$ in place!) I simply close the web page and move to the next item. This is one way to validate my buying estimations. It's also a way for me to test the web site if I have never purchased from them before, see if there is anything that strikes me as odd. Also as an added method of protection I use a pre-purchased Visa with only $5.00 on it, that way if it turns out to be a funky site I lose $5.00 and nothing else. By doing this I can also use a bogus address during the test phase, again as a way to protect myself and test the site.

      Anyhow the next section is the battery breakdown. By this time you should have already narrowed you battery choices down to a brand, voltage and AH rating as well as the configuration you need. This section is for you to validate your load / run times as well as ensure that when you start selecting solar panels (and wind turbines as well, hell even pelton wheels!) you are selecting enough to replenish your batteries. So you enter the following information, manufacture and model, voltage, AH Rate, quantity, how many in series (this will give you your system voltage) and how many sets in parallel to get total system AH. Once this is done you move to the next section which is the load!

      In the load section you enter the nomenclature of the item that is the load, the voltage the amps and how long you think it will run. All of this information should be readily available from earlier research you should have done by now. Anyhow this will give you your total watts, kW and amps requirements. In column|row G26 your total daily power demand will be auto-calculated, below that you need to enter what you estimate to be system loss due to inefficiency as well as line loss. 10% is generally a pretty good number to start with. This will auto-calculate your total load below and this is what you need to make up every day with your solar, wind or pelton wheel. Now keep in mind as I said in earlier posts everything you have is theoretical you may see better performance or worse performance of your system and that all depends on weather, temperature, quality of equipment, quality of connections and installation and just luck of the draw. All the numbers I have listed assume realistic worse case scenarios and chances are pretty damn good I will see much better performance than I show on paper.

      When I ran the numbers for the existing system I have now, they showed far worse performance that I am seeing. Although the exception to that is on really cold and cloudy days the system is performing almost exactly as my worst case scenarios predicted. So I suppose in the end it's a wash. Now the one thing I didn't do was account for the wind turbine in my scenario that you will see in the planning spreadsheet. That is because the wind turbine will not come into significant play until the winter. Sure right now it will produce power but that is diminishing as we move into spring. Fall and winter is where I will see the real production capacity of my wind turbine.

      Alrighty I have rambled enough, the next area is the panel capacity cost analyzer. This is where you search the web for solar panels that meet YOUR requirements. I need panels that will charge a 24VDC system so therefore all my panels that I have selected are rated 24V+. you really need to get accurate data here... otherwise you could very well under power you system. Generating more than you need is not a problem, with a load diverter you don't have to worry. Remember during the summer you will produce far more than you will consume, if you designed your system correctly. And during the winter you should hit on the nose or slightly over with your production to use ratio. Some will argue this is a poor way to design systems... but then again those people are also grid tied. I am not so therefore I have to follow a completely different paradigm than grid tied folks. And if you are looking to be off grid you will have to follow the same paradigm I am.

      So with the cost capacity analyzer you will need to enter the panel manufacture name and model (well you don't have to... but that'll sure fuck things up for you later!) then what type of panel is it. Remember monocrystaline is the best! But it's also generally the most expensive! Next enter the individual panel wattage, volts and amps (the amps are the most important aspect as they determine actual charge capacity!) next you enter the panel quantity and the unit cost (individual cost or if sold as such the pallet cost). Now once you have done that the sheet will auto-calculate sub-total, tax, shipping, total cost, total amps and total watts. In the time slot enter the estimated full sunlight of the shortest solar day of the year. Again you are planning for the worst return on power. Once you do that then total amp will auto-calculate which tells you how many amps you will generate. This is important as you need to replace the amps you consumed. So the spreadsheet will then auto-calculate the power balance, in other words it will take your estimation of daily power consumption and subtract your estimation of power production. The closer to zero you can get the better. If you go negative then schweet! The next field you will enter data into os the source / URL from whence the panels may come.

      Now continuing across the sheet you will see a cost per amp and cost per watt calculation. The lower the cost per watt the better, but you knew this already! So what I do is I sort by the actual cost difference then I look at the power balance and the cost per watt. Sometimes you will pay more overall but it washes out in the cost per watt AND you are close to or below zero on your recharge capacity.

      And there ya have it! Play with it and see what you come up with and if you find an error or have a question as always ask and let me know so I can correct it.

Link to the planning spreadsheet: http://www.4shared.com/office/DKs7vhoI/file.html

      Peace, Love and Five Finger Death Punch!!!