Need to create a wind / solar system which outputs 48Vs:

Re: Need to create a wind / solar system which outputs 48Vs:

You are missing a charge controller (Outback's MX 60 is considered to be one of the best MPPT). But any good MPPT controller (probably sealed construction) should be fine. I believe you will need two charge controllers, one for the solar panels, and another for the wind turbine (plus you may need a "dump" load for the wind turbine controller).

You can look for AGM batteries--properly maintained (good charge controller with temperature compensation) will be much less maintenance (no distiled water needed to refill the batteries).

Also, a good battery monitor would be helpful to ensure the batteries are properly used/charged:

http://store.solar-electric.com/metersmonitors.html

Another issue is will the installation be safe from thieves. I would suggest that you check locally for anything to be purchased--it may be cheaper to buy and maintain locally than shipping from the US (or not)...

Also, you may wish to buy less expensive items first to see how the installation survives (plus you could purchase some spares too with the money saved).

Lastly, you may be able to separate the needs for pumping of well water by only pumping (to a tank) when sun/wind is available (may want a linear boost converter too for the DC well pump) with a battery-less system. Only use the batteries for purification and domestic water pressure (if needed).

-Bill

Re: Need to create a wind / solar system which outputs 48Vs:

Simon,

Looks like an interesting project. I sometimes question the settlement of anyone on small spit of land with little in the way of natural resources (water, land, protection against storms) through the use of non-locally sustainable technologies--but I am here and you and your group are there--so I am sure that there are very good reasons things are the way they are.

Anyway, back to your issues... First, it would be best to know your power requirements (watt*hours per day/week/month/by season--if it changes) and the power requirements themselves (voltage, frequency, maximum current, average power for how many hours per day).

Somebody here should have the link to a world map (I could not find it--it has been posted here before) that will help predict how much radiant energy there is in Colombia. The photos have lots of dramatic clouds--hopefully, this does not represent the normal day to day weather of the area.

And we would need to know the available winds (it is hard to get working wind power from winds that are less than ~10 mph sustained--and pretty much impossible below ~6mph or so).

Also, are there any special issues... I see that only "renewable power" is allowed in this reserve... When designing the system, knowing the limits of the requirements (such as 3 days without sun/wind of battery reserve). If this system must always be available, having a backup generator available (gas, diesel) would be highly recommended for emergencies.

Again, breaking up the pumping requirements--those that are required for pumping to raw storage (which can be done only when sun/wind is available) vs the power required for the RO unit.

Is it worthwhile to collect & store rain/surface water for later filtration (less power required for fresh water than salt for RO).

Would it be a good idea to also support lighting (CFL) for one or more buildings? Much of the time, if the system is designed to ride through poor weather/power collection, there will be excess power available to support "optional loads".

Just out of curiosity, how much water (fresh from fresh or from salt) is needed and how much power is required to produce a gallon of water from the various sources?

Is there also a budget for the parts and maintenance? Solar panels are (obviously) expensive. Wind Turbines don't seem to last very many seasons before needing major overhauls and/or replacement (plus a way to access the turbine at the top of the mast--crane or tilt mast). The typical batteries will only last 3-10 years (depending on price, usage, and maintenance).

Are you going to be able to place this in a container (keep salt air/humidity to a minimum)--I grew up on the coast of California--anything near the coastal fog needed lots of TLC. It appears that the RO (and power?) will be installed near the visitor's center--so the equipment will be away from storm surges. Panels and towers protected against blowing debris?

Will you be allowed to install a tower for the wind turbine (need to be well above any local obstructions and up in the air flow to get good winds).

It sounds like a very interesting engineering project--weighing all of the possibilities vs money and resources available.

-Bill

Re: Need to create a wind / solar system which outputs 48Vs:

Just some back of the envelope calculations for Reverse Osmosis. Using the numbers from small units intended for boats:

http://hrosystems.com/reverseosmosis/brochure.html

Their Escape 400 model produces about 17 gph (65 liters per hour) or 400 gallons per day (1,515 liters per day). Requires roughly 7 amps at 24 VDC (0.33 hp motor).

Assuming that 7 amps * 24 vdc * 1 hour = 15 gallons of fresh water (no UV disinfectant, no low pressure feed pump for pre-filters). (Note brain freeze here--started with 17 gph, used 15 gph below--BB)

(7a*24v*1h)/15 gph = 11.2 watt*hours per gallon (seems to be about right compared to a "15 watt per gallon" you spoke of in one of your links (I assume 15 watt*hours is what you really intended. And another place looking through the web showed about 1 Amp*hour per gallon for an, assumed, 12 vdc system).

Assuming you have good sun and weather (using San Juan PR as closest US solar data near Columbia):

http://rredc.nrel.gov/solar/pubs/redbook/PDFs/PR.PDF

Using a simple fixed array would give about 5.5 kWhrs per day per sq. meter... Or, roughly 5.5 hours per day of sun. You were thinking of 6 x 200 watts of panels, which would give about (at 85% derating PTC/STC of real-life vs lab rating of panels)

Solar Power per day = 6 x 200 watts * 5.5 hours per day * 0.85 = 5,610 watt*hours per day

Amount of water produced using solar panels only:

(5,610 watts / 11.2 watts per gallon) * 0.80 for battery charge eff = 400 gallons per day (average over 1 year).

Is this, roughly, the amount of water you were expecting? Wind will provide more energy--but pending understanding the wind profile of your site--I would assume that you would only use wind as "make up" power for stormy weather at this point.

The cost of the water, just based on the cost of electricity of ~$0.25 to $1.00 per kWhr (typical range of costs for Off-Grid power of solar--capital costs/life-- and generators--cost of fuel/excluding capital costs--excluding costs of managing/procuring non-indigenous supplies for use in Colombia):

5.610 kWattsHrs * $0.25 per kWhr / 400 gallons = $0.0035 per gallon
5.610 kWattsHrs * $1.00 per kWhr / 400 gallons = $0.0140 per gallon

Assuming 1 gallon per day per person per year--Just power costs would range $1.28 to $5.11 per year per person.

Using one of the viral, disposable, filters (assuming sweet water supply), guess at $60 per filter (wholesale) and 3,000 gallons life, and 1 gallon per person per day per year:

($60 per filter / 3,000 gallon per filter) * 1 gal per person*day * 365 days per year = $7.30 per year using non-salt water and personal viral filter

You mentioned that there could be a water supply less than a mile away--although it was not year round (?). It seems that a low(er) tech solution of pump/storage/sand filter + personal viral filter (or even chlorine generated from salt water + electricity to limit the need of a viral filter) may be at least as cost effective, good use of local labor (building/maintaining pump/storage/sand filter/distribution system) and supplying a one personal viral filter per person every 5-10 years. Plus, it could be sized for irrigation of home gardens and animal needs (if this is a need). An RO system would seem to be difficult to justify for agricultural use.

Granted, all of the above are based on SWAGs (Scientific Wild A$$ Guess)--But I assume that RO units are not cheap to buy and maintain either...

-Bill

PS: I see I had a brain freeze above... the unit's rating is 17 gph, not the 15 gph that I used through the calculations. I will leave the above as is--It is still within 10% of the range guesstimated--Solar/Wind/system variability is much more than this (plus you would probably need, at least, another 10-20% power for the feed pump to supply the pre-filters and UV/Disinfectants).

Re: Need to create a wind / solar system which outputs 48Vs:

Simon,

I am sure you know more about the fresh water problems than I -- However, that has never prevented me from adding my two cents worth...

I still believe that low-tech for water treatment is going to be a better place to start in a small, cash poor, village. What are your comments on using a solar still such as the project here? (article talks about trying various low and high-tech systems in southern Africa--Botswana):

http://idrinfo.idrc.ca/archive/corpdocs/049547/index_e.html

It also appears that they could be built small enough to be constructed/operated on a per family basis to generate fresh water (4-7+ Liters per day per sq. meter of collector surface). You still may wish to supply some secondary local treatment (chlorine, viral filter, etc.) but it seems that this would not be the worst first step out there.

The paper is now over 20 years old, so many of the cost assumptions have changed (price of oil and technology). Their conclusion was that these small stills were not the best end-solution, but were a good start on the way to a better life and further development in the villages.

-Bill