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A Wholly Different Approach to Power Conditioning

Yesterday, at Northern Arizona University's "renewable energy fair", I stumbled across a method of power conditioning (generating sine waves) that might be more cost effective than the existing "audiophile choices". People who use solar power, or solar supplemented by the grid, employ these "charger-inverters" that generate a pure sine wave off of DC power. There are 4 or 5 brands out there, but 4 are owned by one parent company, Xantrex. Xantrex tells me that the cleanest unit is made by Prosine. Their models range from 1000 to 2500 watts. For instance, the 1000 watt unit will pass 20 amps peak, and will create a sine wave at full capacity with no more than 2-3 percent distortion. Unlike the PS Audio units, which generate a lot of heat (I may be wrong, but I think they are only 50% efficient), the Prosine charger-inverter is about 90% efficient. You get this for a retail price of about $1 per watt. So if your total system uses less than 1000 watts, you spend about $1000 on the charger-inverter (street price may be slightly less). As I noted above, they tell me the unit will pass the full 1000 watts without significant distortion of the wave form.

What would the advantages of such a system be? To some extent, cost. A PS Audio 1200-watt unit retails for $4000 (substantially less used), and from what I hear, requires some headroom in the energy it produces (i.e. you don't get the full 1200 watts). With this alternative, one would need to purchase both the charger-inverter and a battery bank capable of storing an evening's worth of listening for your system (actually twice that so that you don't often draw the batteries down beyond 50%). You can set up the charger-inverter so that if the batteries do fall down below a given storage, it automatically switches over to the grid and provides power via your local electric company. This would not happen often, but it's nice to have a backup. Batteries should cost around $300, so total system cost is $1300. Disadvantage - you have to keep the batteries outside your living quarters (fumes and such) and check the cells monthly for topping off with water. Advantage - if you live in a sunny area, you can add solar cells to the system and gather your own power. Advantage - you can also purchase a programmer unit and refill your batteries at off-peak times, thus saving about 20% on power. If you like, you could expand such a system to much of your household, thereby saving 20% on your power bills. If your fridge were included, you'd probably need to put a filter just upstream of the fridge.

To me, an Arizona resident, this is an intriguing option. Even without solar, it seems to make financial sense. Unfortunately, solar panels are still pretty pricey. One that generates 120 watts costs about $500, and given the standard assumption of 6 hours available sun during the winter, you would need two of them to store up 1.4 KW-hour for an evening's listening session. So, if you go solar, your total system cost is $2300. Unfortunately, given the utility likely charges about $0.15 for your daily 1.4 KW-hour, it would take 18 year to pay this off!!! Now we are getting into solar issues. An efficient household can run on 4 KW-hours. Conceivably, if you buy more batteries and 4 more panels (total cost somewhere near $7000), you could go off the grid entirely (using gas/propane for heat and drying clothes). Something to think about… ask TWL!!! The payback period for going off the grid might be on the order of 35 years or so - but you get clean power for your stereo!!!

Anyhow, back to the $1300 investment for a battery bank and a charger-inverter. I would love to hear what those who really know electricity, and have the time to check out this sine-wave generating charger-inverter, to get technical responses as to how well they think such a unit would work. Of course, with all those batteries sitting around, you could run some equipment off of pure DC (Hi again TWL).

The following link shows the specs on Prosine's 2000-watt unit. I couldn't find internet specs on the smaller unit. http://www.xantrex.com/products/product.asp?did=255

Thoughts? Impressions?
peter_s
jax2
3,031 posts
 
Hey Peter-

Great idea! My brother in Vermont has his entire house running on large solar panels hooked to a large bank of batteries in the basement. They claim the batteries can last for three days of average use should the grid fail. He also heats his water through the same panels. I had no idea the power was so stable. I'll forward on your post to him and get his impressions (he's an electrical engineer). Look forward to hearing input from those in the know here.

Marco
lak's avatar
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lak
3,516 posts
 
Personally speaking, I think the idea of DC power is a good one, as I have emailed with Twl (in the past) about the concept. I think it’s possible the power could be cleaner than what I achieve with my AC power filtration system (which now does a very good job).
My concern is how much will it cost to purchase the necessary equipment to convert a system (or partial system) over the DC power system? $1300 is probably a good guess.
I’m also aware that many of us have large wattage consumption systems (I don’t), or don’t have the space for the necessary batteries with short wire runs, or have invested large sums os money into AC power therefore are hesitant to spend additional money (or don’t have it).
I would love to hear my system on DC power compared to my AC filtration system to see if it sounded better and by how much.
I do know that the correct sine-wave generating charger-inverter is imperative, and I don’t know how the Xantrex would compare the excellent Studer inverters.
twl
3,251 posts
 
Yep, I use the Studer Inverter for the stuff that I can't power directly off the 12vdc from the batteries. I don't know exactly how the Xantrex compares to the Studer, but as long as it is clean, then you're ok. You MUST use a FULL-SINE WAVE inverter. Modified sine waves like the cheaper inverters produce are noisy as hell, and not suitable.
sean
6,229 posts
 
3% distortion is not too good. Your AC as supplied by your power company is supposed to remain lower than 5% at any given time. If it is above 5%, chances are, your pole transformer is defective. In comparison, the PS units are probably WAY, WAY below this, but i'm not sure. They don't post any specs on their website, so who knows. Sean
>
twl
3,251 posts
 
Sean, I think you'll agree that the issue is not necessarily what the power company specifies, but what is actually on your power coming into your house. The distortion they generate, is simply the baseline to which all the other crap from all over your neighborhood, and in your house, is added.

By creating an isolated power supply from battery, and a controlled AC inverting system, this creates a much cleaner, better regulated, and lower distortion supply, which is not subjected to all the other problems the mains lines are subjected to. It is a controlled, isolated, closed loop system.

Also, if you want to use a separate inverter/battery for each component, even the power supply intermodulation between components could be eliminated. This is something that is not often addressed, but is present in most systems.

I know you can't use a system like this with a high-power audio system, due to power drain considerations on the batteries. But for a low-power SET amp, and a typical preamp, it works great.
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