Any and all feedback greatly appreciated

System

Hi my name is Jeff (hence the screen name) and I’m a solar noob.

Sorry for the long post, I just wanted to try to present as much info as possible.

Here's the story: I purchased some property in the Sierra Nevada foothills that features a 3 acre bass/sunfish pond. Eventually I am going to build a retirement home on the property and escape the mad city life. (I know another urban refugee). When I build the home I am going to use either a grid tied or off grid solar system. I am still in the process of discussing that with solar professionals - - that’s way too large of a project for this bean counter to muck with.

But back to the issue at hand – the pond. I have determined that I need to aerate the pond so I have been looking into alternatives. At this point an AC power line is not an option because of the cost. So I have two choices a windmill aerator or a solar power aerator. The windmill aerator is not really relevant to this forum so I won’t get into a discussion about that here. Sorry to bore you with all of this detail – I’m just trying to provide some background info. I have read lots (and I do mean lots) of info regarding solar energy and downloaded a PV system calculator (excel spreadsheet) and manual spreadsheets and calculated the system requirements using both. Unless I’m a total solar moron (which is a very plausible possibility) I have calculated the system cost to be over $6,000 YIKES.

I have been lurking and reading this board for a few weeks now and have enjoyed the feed back that you give others so I’m hoping that I can use some of the members technical expertise on this project. As a side note I currently have a travel trailer on the property that I have a small (ok miniscule) solar set up to run 12 volt lighting and fans. I have two 11 watt solar panels that charge two 12 volt batteries. The panels are the flexible kind (sorry forgot the brand name) that have a built in charge controller. This system has been working perfectly for the limited use that I put it through.

Ok once again sorry for the long winded explanation (I hope you are still with me here), on to the calculations:

One additional fact is that the system will only be used in the months of May through probably September (no need to aerate in the winter). I have a great area to place panels in full sun with no shade obstructions.

PV Energy Needs:
The lowest energy consuming air pump that I could find (that will provide adequate air pressure) consumes 140 watts (115 volts at 1.22 amps). Assuming that I want to run the pump for 12 hours per day, that results in 1,680 watts per day. The worksheet calculates an AC inefficiency factor at 25% so with that increase I get a daily PV budget energy budget of 2,100 watts. Diving this by 12 system volts I get 175 daily amp hours.

Battery requirements:
175 daily amp hours times three days of automony = 525 normal storage capacity in amp hours. Using a 50% maximum drawdown then my required battery capacity of 1,050 amp hours. So using a Concord PVX-258 Sun Extender battery rated at 255 AH it appears that I will need 5 batteries (1,050/255 = 4.12, which I rounded to 5).

PV Array Size
Total daily amp hour requirements 175 divided by 8 bright sunshine hours = 21.9 array current in amps. 8 hours might be too high but my thinking was that I am only using the system during the bright summer months. Perhaps this is still too optimistic though. Using a Kyocera KC-130 solar panel rated at 130 watts, 7.39 amps, and 17.6 volts it looks like I will need (21.9/7.4 = 2.96) three of these panels.

Here is the budget:
Kyocera KC-130 panels: 3 at $609 = $1,827
Concord PVX-2580L batteries: 5 at $615 = 3,075
Cables complete guess at $50
Controller Xantrex C35 = $100
Inverter Excel Tech XP 600 = $531
Pole mounts TMP-KC130 = 802

Total system cost $6,385.

So assuming you managed to get through that boring and long winded portion of my post here are my questions:

1. Are my calculations anywhere near the ballpark?

2. Batteries are almost half of the system budget. Let’s assume that I decided to eliminate them and only run the system during days and hours of adequate sunshine. Would it be possible reduce to one battery and run a timer to cut system cost down? But what about cloudy days, is there a device that will determine when you have adequate power supply and only run the pump then? Am I making any sense?

3. Finally what do you think of my equipment choices? Any suggestions?

Keep in mind I’m a complete solar novice so you so won’t hurt my feelings with any comments or suggestions. I welcome any and all input.

Finally, thanks for great forum, I know a lot of work goes into a forum like this and it is a fantastic resource.

crewzer

Re: Any and all feedback greatly appreciated

Jeff,

Where in CA? If possible, please select a location from this list:

http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/sum2/state.html

More later,
Jim / crewzer

System2

Re: Any and all feedback greatly appreciated

Jim,

The closest on that list to the property would be Sacramento.

Jeff

BB.

Re: Any and all feedback greatly appreciated

Jeff,

Go to the head of the class for solar!

For how much sun you will have at your location (data is in kW/sqmeter--but since full sun is ~1kW/sq meter, most people simply make the easy transformation from 6.2 kW/sqm to 6.2 "hours of sun"...

http://rredc.nrel.gov/solar/pubs/redbook/ For US (I like the PDF files as the data and yearly variations is easy to see)

And, everything is about conservation of power... So, the first place to look is at the air pump. 140 watts does not sound like much until you multiply it by XX hours per day * solar panel derating * battery charge efficiency derating * inverter derating * weather derating... etc... Your 2kWatts*Hours/day is getting close enough to fully run an efficient cabin/house (lights, fans, washer, well pump, radio/tv).

So, if 140 watts is the best you can do for the pump (not sure--but I would look more and at differing methods of aerating the water--like mechanical beaters and such). This will drive the cost the rest of your system (and if you pay $200 more for the aerator and save $2,000 on the system costs--that would not be unusual).

When you take all of the deratings and multiply them out, you find that you about 50% of your nameplate rating goes up in system losses. So, looking at the losses--

1. Panel derating by temp--Mount panels away from roof (tilted up, on fixed pole). Hot panels generate less power than cool panels.
2. Panel derating by life--If this is a long term installation, I would suggest you go with standard poly or mono-crystalline solar panels. Other types, while advertised as better in hot weather or less sun--are not--and they degrade over a few years, rather than the decades of the p/m-crystalline. (p/m is typically ~20% degrading after 25 years, amorphous is that in a year +/-)
3. Panel Mounting--Tilt them to your latitude (or minus 15 degrees if you want summer only). If you don't have too high of wind in your area, look at solar trackers. They will increase the amount of power you can gather--however, check the brand/model. There can be lots of maintenance and repairs associated with trackers.
4. Wiring--look at higher voltages / larger wire gauges to keep power losses below the ~3% level.
5. Charge Controller--MPPT chargers (maximum power point tracking) works well for areas with cold weather (typically winter when solar panel voltages are higher) and if you have long runs from the solar panels to the charger/battery bank (100 VDC from solar panels is stepped down to 14 VDC to charge the battery using P=I*V sort of like the a DC electronic transformer). Non MPPT controllers are less expensive and work well for moderate temperatures and with "12 VDC" panels connected to "12 VDC" batteries (or 24v to 24v systems too). MPPT Controllers are great for almost anything over 400 watts of solar panels, below that, the power needed to run the MPPT function starts to eat up any extra power recovered by the MPPT function.
6. Batteries--Evil. Can you get away without them? Aerate only when there is sun. Pump water into a tank and let it aerate via gravity when no sun. Use air-stones and such to break up the bubbles and better transfer oxygen to the water. If you cannot live without batteries... Look at AGM batteries. They are ~90% efficient with charging, vs flooded cell ~80% energy efficient. Also, AGM's don't need water, cleaning, or equalization like flooded cell do. Also, some vendor's AGM's can be cycled down to 20% SOC--fewer batteries needed. Down side--very sensitive to overcharging. For anything more than a small system, always get a charge controller with battery temp sensor (battery voltage is very dependent on temperature).
7. Inverter--Get a "True" Sine Wave inverter. A "modified" sine wave (or mod-square wave) inverter is much cheaper but will usually not last as long, be as efficient--especially with AC motors, and some motors/appliances/electronics will not work with mod-sq-wave inverters at all (overheating, interference, wrong frequency--are some of the issues).

To run the pump without batteries, look for something called a linear current booster and look for a DC powered aerator. Most motors, at lower voltages, use much more current to start and run. Solar panels at lower light levels, keep their voltage relatively fixed near the Vmp value, but lose current. The current booster basically is a DC to DC converter that takes V*I of the solar (aay 15v * 1amp) and converts it to what the motor may run on (say 5v at 3 amps). Won't help in all cases, but does work fine where the load of the motor is reduces at lower motor RPMs (like fans, well pumps). May not work as well for fixed loads (like an air compressor).

Issues with DC motors are that most use brushes--and over the long term, you will be replacing brushes every x,000 hours of operation.

You could also run a system with a timer, or even a battery monitor that could give a signal when the batteries are drained to a certain point:

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

There are also controllers that have Low Voltage Disconnect setpoints that you can use to control and external switch/relay/FET.

You can certainly ask about wind in this same thread since it is for the same project... Although there is another place here for wind discussions too.

-Bill

Roderick

Re: Any and all feedback greatly appreciated

Hi, Jeff.

I'm a big fan of solar, and if that's the way you want to go, there are others here to give good guidance.

I just wanted to raise some interesting questions.

Are you sure that you really need to aerate your pond. Does it smell? Did you want to support more fish in it? Tilapia don't need a while lot of oxygen in the water to survive, for example, but I know, some people don't like the taste of Tilapia. Could you accomplish your pond cleanup by planting something like cattails or water lillies?

Also, is there grid power on the property, already? If so, would it be cheaper to just run grid power to your pond?

It sounds like a lot of trouble, maintining batteries just to aerate a pond. What if you went with no batteries, just direct connect to the pump? If it's a cloudy day, and the flow is low, is that fatal? If there isn't aeration for 3 days, is that fatal? I don't know, just some thoughts.

crewzer

Re: Any and all feedback greatly appreciated

Jeff,

1. Are my calculations anywhere near the ballpark?

2. ... is there a device that will determine when you have adequate power supply and only run the pump then?

3. Finally what do you think of my equipment choices? Any suggestions?

140 W x 12 hours/day = 1,680 Wh/day net. Assuming 87% inverter efficiency, the energy input to the inverter will be 1,931 Wh/day.

The Exeltech XP-600 is a good inverter, and its internal fan cooling may be a benefit in your location. For a dedicated system, you might also consider the XP-250 model, but make sure you install it vertically to promote good passive convection cooling.

Allowing for thee days of autonomy and a maximum discharge of 50%, you’ll need a 12 V battery bank rated at (1,931 Wh/day x 3 days) / (50% x 12 V) = 965 Ah. Four size 8D batteries (~250 Ah each) should work. In addition to Concorde, check with Deka, MK and Trojan for AGM batteries.

Working in Ah, the batteries will be required to deliver 161 Ah/day. The coulombic efficiency of AGM batteries is ~98%, so figure they’ll need 164 Ah/day to recharge.

Tilting your south-facing array at ~23-1/2 degrees in/near Sacramento (latitude - 15 degrees), average monthly “summer” insolation will range between 6.5 and 7.8 hours/day. Using the lower number, your PV array will need to be able to deliver 164 Ah/day / 6.5 hrs/day = 25.23 A. Assuming “12 V” modules rated at 17.6 Vmp, you’ll need an array rated at 25.23 A x 17.6 V = 444 W (STC).

This timer might work with just about any controller: http://store.solar-electric.com/fldctico.html

An alternate controller with a built-in “timer” might be the Morningstar Sunlight 20 w/ low voltage disconnect. See: http://www.morningstarcorp.com/products/SunLight/index.shtml

Bill’s made some good suggestions. You could forget batteries and multiple inefficiencies altogether by running a DC pump from the PV array using a linear current booster. See: http://store.solar-electric.com/7amplincurbo.html

For example, would a system comprised of a couple of ~100 W PV modules, a couple of linear current boosters, and a couple of DC pumps work for you?

HTH,
Jim / crewzer

BB.

Re: Any and all feedback greatly appreciated

I forgot to mention, also check for shadows--none between 9am-3pm is a good start. Also look for trees/wires/building on nearby properties, etc. May not be a big issue in a rural community, but in the city--very much an issue as Solar PV panels don't do well with ANY SHADING AT ALL (50% or more loss of power with only a little shading is very likely).

-Bill

System2

Re: Any and all feedback greatly appreciated

First off thank you all for your feedback regarding this project.

Here are some answers to your questions and comments and way too much additional information:

BB:
“Everything is about conservation of power.” Boy I have learned this during this process. It’s kind of funny that when we are staying at the trailers on the property we use so very little energy – 12 volt lighting and fans run mostly only 2 to 3 hours at night. Hence the miniscule trailer solar system.

The air pump story:
The air pump that I have chose is the most energy efficient pump that will provide the required volume of air flow at the required PSI to aerate my pond to the depth that I need. What I failed to mention in my initial post is that the pond is 17 feet deep, and in order to get enough air flow down to that depth to provide enough air flow to a diffuser (actually two diffusers because of the volume of the pond) it requires a fairly significant air pump. The pumps originally suggested by the pond gurus gobbled up between 253 amps to a whopping 460 amps. This would have made my solar budget to through the roof! So I researched like crazy to get a pump down to 140 amps. Unfortunately none of the DC air pumps will provide anywhere near the air flow at the required PSI to overcome the depth of the pond. You mentioned mechanical beaters for aerating water, unfortunately they don’t aerate water much beyond about 4-5 feet deep which will not be sufficient for my pond depth. (I know probably way more information than you wanted about air pumps and ponds).

System losses:
Great information, thank you. As a side note when at a recent building show I spoke to several solar companies regarding the eventual home construction – they all said the same thing about panel derating by temp. I had found solar roof shingles that I thought looked nice but according to all the solar companies those are not advised unless you have no where else to put panels mainly because of the temp derating problem – something I had never heard of before. Fortunately I have 30 acres of property and there is a nice clear (of vegetation) crown of a hill that will get great exposure for the eventual house installation.

Evil batteries:
Thank you for the suggestion of the alternative brands. By switching to an AGM battery I can cut my budget for the batteries in half.

Shadows:
Fortunately at the pond site there is a rather large meadow area at the east end of the pond that doesn’t have any trees, power lines or anything else that will cast a shadow – aside from the occasional turkey vulture.


Roderick:
The pond story:
The pond was built sometime during the 1940s and was virtually never maintained. According to some of the pond gurus that I have spoken with without any intervention (aeration or filtration) most ponds have about a 30 year life. The saving grace with this pond is that it is spring fed which replenishes and renews the water. The pond is stocked with Large Mouth Bass, Green Sunfish, Blue Gill, Red Ear Sunfish and a few Catfish. In northern California we are not allowed to stock Tilapia. The pond is beginning to suffer from muck build up. Vegetation has formed a layer on the bottom of the deeper area’s of the pond that are not decomposing due to a lack of oxygen. Hence the aeration. Since the pond is deep I need to move a significant column of water up from the depths to the surface. The most efficient (from a water movement perspective) method to do this is to use diffused air to create a moving water column. The pond does not smell but is beginning to get clogged with vegetation and algae. I can (and will) use chemicals (there are several good herbicides that will not harm animal life) to kill back the offending plants but this is a short term fix. In addition during chemical vegetation removal you have to be very careful about causing an oxygen crash. Getting the muck to decompose will (purportedly) reduce the algae and Elodea and will reduce the likelihood of a fish kill due to an oxygen crash. Mainly the aeration is to help renew and rejuvenate the pond.

The pond is at the end of a valley and is the only year round surface water in the area. As such it is a great resource for wildlife and my intent with the property is to create sort of a natural wildlife sanctuary. I do fish but am not a hunter (don’t have anything against hunters but just never had the stomach for it myself). I myself have personally observed a lot of natural wildlife using the pond including: deer, mountain hare; red fox; turkey; squirrels; heron; geese; ducks, etc. In addition I have found (but never viewed) mountain lion tracks and bear have been seen on the property by a neighbor. The intent is to build a low impact energy efficient home and keep the property as natural as possible and just enjoy the wildlife and to fish on the pond.

Grid power:
No grid power exists on the property as yet. The nearest power pole to the pond is probably 1,200 to 1,500 feet. I may eventually have grid power to the house site which will be about 300 feed to the pond, so it maybe merely a waiting game until the house is built.

Running the system with out batteries:
Funny you mention that. This seems to be the most cost efficient solution. Although in theory it is better to aerate at night it seems like it will be way too expensive. Any aeration is better than no aeration so I have recalculated my system using a six hour per day run time that will only run during the day light hours and not on cloudy days. This reduced the budged to $2,465 – much more acceptable.

Jim
Thank you for the education, equipment suggestons and fine tuning my calculations. I have modified the excel spreadsheet to use an 87% inverter efficiency (instead of my 75%) and to use a 98% efficiency for the batteries and to use only 6 hours of summer isolation.


Revised calculations and budgets

Using Jim’s tweaks to my original calculations I have determined revised numbers as follows:

Here is the revised budget:
Kyocera KC-130 panels: 4 at $609 = $2,436
AGM 8A40 batteries: 5 at $329 = $1,645
Cables complete guess at $50
Controller Flexcharge DC Timer Controller: = $72
Inverter Excel Tech XP 600 = $531
Pole mounts TPM-2-KC130: 2 at $265 = $530

Total system cost $5,264.

Much better than my original $6,385. Still fairly costly.

A redesign
So back to the drawing board. Based upon all of your input and using the theory that any aeration is better than no aeration I decided to re-design the system entirely. Run the air pump only during the day and only for 6 hours per day. Here’s the resultant calculations. Load calculation: 140 watts x 6 hours per day divided by 87% inverter inefficiency = 966 daily watt hour divided by 12 volts = 80 daily amp hours. Battery calculations: 80 amp hours divided by 50% max battery draw down and divided by 98% battery inefficiency = 164 battery capacity in amp hours. Using a AGM 200 AH battery will require only 1 battery. PV Array Size calculation: 80 daily AH divided by 6 bright sunshine hours = 13.4 array current in amps. 13.4 divided by 7.4 module current in amps = 2 modules required.

Here’s the budget with only a 6 hour per day and day time only run times:

Kyocera KC-130 panels: 2 at $609 = $1,218
AGM 8A40 batteries: 1 at $329 = $329
Cables complete guess at $50
Controller Flexcharge DC Timer Controller: = $72
Inverter Excel Tech XP 600 = $531
Pole mounts TPM-2-KC130: 1 at $265 = $265

Total system cost $2,465.

If my calculations are correct that is much more affordable! Using a prepackaged windmill style aeration system is still slightly cheaper in total but has the problem that it simply will not run without adequate wind speed – I’m still researching this option. I am going to have to measure wind speed near the pond.

Any comments regarding the six hour run time calculations and budget?

Wow, I can't thank you all enough for your input and education - this is forum is truly a great resource. I will keep you posted on this project and others and will continue to participate in forum in whatever capacity I can (being a solar ignoramus I can’t provide any technical advise) but I will chime any on anything that I can. Because of the huge pending house project I am going to sign up some solar energy courses - not because I want to be involved in the house system design (I'll leave that to professionals) but merely because I feel like I need to understand how the system will work.

Sorry once again for the long winded post.

System2

Re: Any and all feedback greatly appreciated

Oh and as an also and besides I have several other projects in the design phase including a solar well pump to fill a holding tank for the trailers and a solar powered workshop (ok maybe I'm dreaming with the workshop but a guy's gotta dream don't he?).

If your interested in seeing photos of the lake you can look at my amateurish attempt at a web page. Some of the info (fish stock) is a little out dated but it does have a few good photos.

http://www.hiddenlakeranch.us/

Jeff

System2

Re: Any and all feedback greatly appreciated

Mu uncle, in his younger days, had 3 fish ponds. He aerated his ponds with a small water pump, which sucked water from near the bottom and sprayed it up into the air, to fall back onto the pond.
Don't remember the exact details of the pump, but wasn't all that energy sucking.

BB.

Re: Any and all feedback greatly appreciated

I too was going to suggest the water pump route too... Mixing from top to bottom with the water pump and using a low(er) pressure air pump (or other aeration options like pump from bottom and spray--again with solar only power) should help a lot.

Looks like a slice of heaven...

-Bill

niel

Re: Any and all feedback greatly appreciated

if my memory serves correctly, i believe they have windmills that are used to move water without the need to convert to electrical power and then back to mechanical, which would be innefficient. if you have long periods without wind then i'll agree with the pv usage to power a pump to use for aeration of the water. i'm no expert when it comes to pumps or water cleansing so i draw the line here in my advice.

crewzer

Re: Any and all feedback greatly appreciated

A redesign
So back to the drawing board. Based upon all of your input and using the theory that any aeration is better than no aeration I decided to re-design the system entirely. Run the air pump only during the day and only for 6 hours per day. Here’s the resultant calculations. Load calculation: 140 watts x 6 hours per day divided by 87% inverter inefficiency = 966 daily watt hour divided by 12 volts = 80 daily amp hours. Battery calculations: 80 amp hours divided by 50% max battery draw down and divided by 98% battery inefficiency = 164 battery capacity in amp hours. Using a AGM 200 AH battery will require only 1 battery. PV Array Size calculation: 80 daily AH divided by 6 bright sunshine hours = 13.4 array current in amps. 13.4 divided by 7.4 module current in amps = 2 modules required.

Here’s the budget with only a 6 hour per day and day time only run times:

Kyocera KC-130 panels: 2 at $609 = $1,218
AGM 8A40 batteries: 1 at $329 = $329
Cables complete guess at $50
Controller Flexcharge DC Timer Controller: = $72
Inverter Excel Tech XP 600 = $531
Pole mounts TPM-2-KC130: 1 at $265 = $265

Total system cost $2,465.

Jeff,

1) The DC timer controller is not a charge controller (to go between the PV array and the battery bank). You’d still need a charge controller.
2) What will happen after one overcast day (no significant insolation)?
3) What will happen after two overcast days in a row?

HTH,
Jim / crewzer

mike95490

Re: Any and all feedback greatly appreciated

Grid power: No grid power exists on the property as yet. The nearest power pole to the pond is probably 1,200 to 1,500 feet. I may eventually have grid power to the house site which will be about 300 feed to the pond, so it maybe merely a waiting game until the house is built.

Just curious, Is that power 1,500' away on a neighbors meter ? How much ext cord will $5K buy? Keep the neighbors fridge stocked with 6 packs ?