Feasibility of Solar Panels for Hidden Grow Room setup

I've never grown before, so the idea below is conjecture. It is subject to modification based on the input of others who have grown weed.

I know not the cost to really start a growing operation, but I'm going to give some basic input on a renewable energy system. It will be subject to modification as I recieve input.

I basically want to design a fully renewable energy powered marijuana growing system that has a payback period of < 4 years.

I know how to work with solar/wind power and electrical components as well as design them, you guys know how to work with weed. As suggestions are made in this topic and as I learn about grow setups, I will compile a design for a grow room, run through a cost analysis, figure out how much weed it will make, and when all is said and done, a new topic can be made detailing the setup as a whole and how to build/test it. I have Orcad on my computer and can run simulations of everything. Maybe even design some automated control systems and test their stability with the Routh Hurwitz stability criterion and do a few Bode plots...

We all like the idea of growing without and electric bill to worry about, and there are types of roof shielding available to prevent helicopters from peering in your home and detecting temperature with infrared cameras.

So lets help each other out. Below is a sample proposal:

=========================================


It's possible to generate electricity from a photovoltaic array for ~$.16-.22/kWh, counting in inverter and flooded lead acid battery replacement costs. If solar panels were produced in higher volume, price would drop. Most areas in the U.S., coal is used to make electricity at about $.05-.07/kWh but the consumer is generally charged about $.10-.15/kWh. Solar panels have a rated lifespan of 20 years by industry, but in reality, can last over 40, which would greatly lower electricity cost.

Wind is cheaper than solar. Over the life of a small turbine, electricity can be made for about $.04-.06/kWh, around $.10/kWh counting inverter and battery. The problem with wind is that it only generates real power and not reactive power. This is easily solved by power factor correction.

Alternative energy is perfect for a hidden grow operation. I will elaborate why.

you don't want this grid tied, so it will need batteries and a DC-DC converter to charge them from the panels, and an AC to DC inverter to run your equipment off the batteries.

Unless you can find suitable LED style lightbulbs, the most energy efficient and cost efficient lighting in the long term for growing pot is perhaps sodium vapor. They produce about 100 lumens per W, so a 400W light would do about 40,000 lumens. If you have a small 2ft by 2ft grow patch for 4 plants, that's 10,000 lumens per square foot. Natural direct sunlight is about 10,000 lumens per square foot, but low light plants can thrive in 1,000 lumens per square foot environments. You don't want to burn the plants and want a relatively even light distribution, so placing the light about a foot above them will reduce this to about 2,500 lumens per square foot. Assuming the plants are about 80% at absorbing the light and the walls of the room are sufficiently reflective to allow this, that's 2,000 lumens per square foot. This is suitable.

We'd need about 18 hours of lighting a day for high potency plants that mature about 5 months in. This is 400W * 18 hr = 7.2 kWh per day for lighting.

Water and air pumps will run about 20 hours a day drawing ~20W total, for .4 kWh. Fans, another 20W for 20 hours for .4 kWh.

So that's 8 kWh of electricity needed each day for the grow op.

The U.S. receives the equivalent of about 6 hours of direct sunlight a day spread over the duration of daylight, more in the summer, less in winter. 8 kWh / 6 hr = 1.333 kW system needed. This is not yet factoring battery, inverter and DC-DC converter efficiency, so this number will later be modified.

DC-DC converters are about 90% efficient and in the neighborhood of $1 per peak watt. You'd want something at least as large as the panel setup.

The batteries, you'd want at least enough capacity to last 2 days, in case the weather is not favorable to sunlight. Flooded lead acid batteries are the cheapest and most cost-effective option for this type of operation. You can buy Trojan T105s, rated to 225 AH at the 20 hr rate and 6V nominal, which is 1.35 kWh storage each, for about $75. They are about 80% efficient when charging and will last about 5 years in this application.

The inverter will cost about $.15 per continuous watt. You'd want one large enough to to run all loads at the same time continuously, so that's about 500W, or a $75 inverter. Xantrex makes a 500W cont, 1,000W peak inverter for roughly that price. They are about 90% efficient.

So a 90% efficient inverter means you need a battery pack that can supply 16 kWh for two days, divided by the .9 inverter efficiency. So that's an 18 kWh battery pack, or 13 batteries. Which is $975 for batteries.

The DC-DC converter will need to be large enough for the panel setup and to account for battery and inverter losses. 1.333 kW / .8 / .9 = 1,850 W. That about $1,850.

Solar panels are about $4 per watt. You'd need an array large enough to account for DC-DC, battery, and inverter losses, so 1.333 kW / .9 / .8 / .9 = 2,000W. That's $8,000 in solar panels.

So lets tally it up. That's $11,000, not yet counting the lighting, pumps, fans, and the rest of the grow op setup. Add about $1,000 for that, as sodium vapor lighting is not cheap.

So $12,000 or so.

This may be a huge sticker shock at first glance, but 2ft by 2ft grow space is enough for 4 plants, which will yield about 1.5 oz of weed each, for 6 oz total. If the weed is of decent quality(lets say, 'mids'), which it probably will be with 18 hours of light a day to have a long growth rate, it will fetch about $300 per ounce, $1,800 per harvest. Subtract about $1,000 every five years from your profits to replace the batteries, another $500/year for miscellaneous equipment replacement. Assuming 5 months every harvest, it will break even in about 8 harvests, or 3.5 years. Not too shabby. After that, you will keep reaping in profit, and perhaps spend $1,000 to replace the batteries at the 5 year mark. After the break even point, you're making roughly $3,620/year in profit from this grow op with the solar setup having paid for itself by the 3.5 year mark.

This doesn't include a discount rate, so adjust these numbers for inflation accordingly if you want exact figures. Differential equations are your friend, but either way, this is all in 2007 dollars without a discount rate. If you smoke your profits, you will have to adjust the figures accordingly as well.

If your area is suited to it, you could get by much cheaper with wind turbines. But you'll definately want a larger battery bank than two days electricity storage!

The cost of entry of the solar setup may be daunting, but an experienced grower that knows how to prevent failures can be rewarded nicely. A room dedicated with a 8ft by 8ft grow-op could really rake in some serious money and allow you to love comfortably off of the profits made, without you needing to work. But you'll basically have an entire roof covered with solar panels.

The only problem is, it takes money to make money with this method. Even one measly plant that will give about 1.5 oz a harvest is going to take about $1,500 in goods to get growing grid-free with solar and reliably. If you can manage to grow some good purple haze, the payoff will still be worth it at $500+/ounce. But you'll only be getting about 3.5 oz a year from planting a single plant each time, if you're good at it.

Price of the system can go way down if you're willing to grow less potent weed, say, using only 10 hours of light a day instead of 18. This dramaticlly lowers your power requirements. But it also lowers the quality of your weed if it matures earlier, and you'll get less money for it.

It's up to each individual grower to perform a cost benefit analysis to find a setup to fit their needs.

You could also grow far more plants than 4 square feet on 400W of light, but they'll tend to be lower quality. Cost-benefit analysis again comes into play when optimizing your system. Getting a payback of only 1.5 years may actually be possible, but 3-4 years would probably be more typical for an experienced grower.

 

Thanks for the comments Syrus. I'm going to read up on the spectrums these grow lamps put out and the spectrums that marijuana needs to grow properly. As for payout, lets just assume that I smoke it all then, and instead don't have to buy it.

If you can afford and find blueberry or NYC Sour Diesel, what I've got right now, then get some. I ain't selling mine.

Makes sense. You looked into it years ago, right? Just 10 years ago solar cost about double what it does today. Wind has been feasible for about 15 years, cost competitive with coal and natural gas. The problem is that it is less reliable due to shifting weather patterns, requires some maintenance due to rotating parts, and the generators used don't generate reactive power but only real power. However, with current technology, we could be hacing near 20% of our electricity from wind and consumers would save shitloads, but wind energy has less profit margins than sources like coal or natural gas and therefore the utility industry has widely shunned it. Less than 1% of America's electricity is wind today, which is sad.

It's not as expensive as you'd think, at least if you build your own rotor, generator, AC to DC converter, and other components. With a properly sized battery bank, you don't need no charge controller, and the rectifiers in the AC to DC converter are usually good enough to prevent stored energy in the battery bank from causing your homemade generator to act as a motor and waste your energy. I've built a wind machine out of spare car parts and NdFeB magnets and it worked. 500W(at 30 mph with 8 foot diameter blade) peak machine for ~$500, not counting batteries and other ancillary components. $1 per installed peak watt! If I got more data from testing it, I would have been able to properly size a capacitor and place it in series with the armature so that the resonant frequency of the circuit matches that of the cap, causing the machine to track the optimum performance curve for a given wind speed(Asynchronous AC induction generator). This would double the peak power output to over 1 kW at 30 mph. Then there's laminations that could be added to the stator to reduce eddy current losses.

A 22 foot diameter machine could probably be done for about $2-3k. The trick is to build your own. Depending on your electricity demand and grow op size, it would probably provide way more than you could ever use.

In low wind speed conditions, vertical axis wind turbines show their superiority over horizontal axis wind turbines. HAWTs usually stay stalled until the wind reaches > 10 mph or so depending on design, tip speed ratio of the blades, and other factors. VAWTs, while they use rotors such as Darreus or Savonius which are very inefficieint, have an advantage of high starting torque and can thus made usable electricity from very low wind speeds ~2 mph or so.

It's all about plotting the Rayleigh distribution of the wind speeds in your area, crunching a few integrals, and figuring out from there which design is the best for your situation.


I'll look into the feasibility of this a lot more. In the future, if it seems workable, I'll have to make a topic showing you guys how to build your own wind machines from scratch just for the purpose of growing the sacred herb. After all, we wouldn't be here if it weren't for the herbage.

Toke on man!