Backyard Aquaponics
A place to discuss aquaponics

Hi,

I think that the use of metal halide (or high pressure sodium) lights has two aspects that need to be taken account of when it comes to efficiency.....light and heat.

At the moment, our US friends are suffering a distinct shortage of both.

Gary

[quote]njh wrote:How necessary is artificial lighting in the cooler climates? Has anyone looked into using heliostats or even large white painted walls to increase the photon count to a suitable level for aquaponics?


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[quote] Janet wrote:

Our days are pretty short and dark now, and even folks with good access to sunlight will extend the length of the day with artificial light. For many years, I raised seedlings for the dirt garden during the early spring. The first couple tries were in the sunroom with no artificial lights. (Sunroom walls are white, no heliostat.) The seedlings were all spindly and weak. (tomatoes, capsicums (peppers), and eggplants) When I started raising them under big banks of grow lights, they did wonderfully.

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Yes, we have too few hours of light for 3-4 months at 42 degrees north lat.
I plan some artificial light (as little as I can get away with).

When I designed my building, light and heat were major concerns. So, my walls and ceiling are a dull metal foil on 3/4" insulation foam board. The spec is 97% radiant energy reflection. Good for light and heat. It has been below zero F every night for a week. My greenhouse was 72F today and was at a low of 36F last nite. No artificial heat used. The foil has been very successful with no hot spots. It does a great job of diffusing the light.

For us cold, dark northerners, artificial light is an important topic. I realize MH is best, but the energy costs are prohibitive IMO. The Fluorex were new, high output per watt of broad spectrum light according to their claims and worth investigating.

I won't have plants until the light level is acceptable this spring. My light testing will start next November - 9 months from now. I will try the Fluorex and it would be interesting to use a 150 watt MH on the other end of the grow table for comparison.
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I guess another problem with concentrating the short hours is the fact that plants need longer hours as well as brighter light. It does seem a little worrysome that people are burning so much coal to grow plants - it's not going to help the climate situation.



This is a strange claim, if MHs are more efficient, their energy costs are lower, no? According to:
http://www.venturelighting.com/TechCent ... Intro.html
MHs are more efficient (though there are examples of fluoros that are more efficient than MHs).

The note about temperature dependence seems relevant too.

I'm hoping that the energy burned to light my seedlings was offset by the energy not spent transporting vegetables to the supermarket, and making chemical fertilizers/pesticides/herbicides to poison...er, treat them, before they were shipped. Our season is short enough that you really need to put out transplants rather than seeds for tommies etc.

janet: understood. I expect you're right, especially if you can source low impact electricity (wind?). We have green energy here where you can buy some or all of your electricity from renewables (usually wind or hydro).

I guess we could actually estimate this for coal fired too: if you are using 20kWh/day and trucks are about 400MJ/tonne km which is roughly 0.1kWh/kg km. If the food is being shipped 2000km effective 'food miles' that's 200kWh/kg of food, or 20 days of light per kg produced.

Does this sound reasonable? If you are using lights for 2 months, 60 days, then you'll need to produce 3kg of food to offset your energy cost. That sounds doable.

Check my assumptions.

I checked my grow lights. Full bank is 12 40W tubes. So at full capacity, 18 hours per day, I get a burn of (12 x 40W x 18hrs)/1000 = 8.6kWh/day. Two months on full power is reasonable, given a little ramp-up and ramp-down (=516kWh total). And 3kg of food is easy. Those seedlings would give my parents, sister and me enough tomatoes to can the winter's supplies of tomato sauce and whole tomatoes, plus all the fresh tomatoes and capsicum we wanted. (Total of 6 adults, varying numbers of kids.) Eggplants never did well for us at the time. (We now think the secret is lots of water!)

Well gosh, I'm not going to feel guilty if I need to put a small bank of growlights over one of my growbeds.

I wouldn't either. It's like when I worked out that my extra shower per day was equivalent to 30mL of petrol - just starting a car uses more petrol than I use riding to work

But it is important to check these things! I don't think the same analysis would look so good if the plants were being grown to maturity under lights.

Thank you for the link, looks good (I will read it soon).

I am having trouble following your logic....MHs are more efficient....fluoros are more efficient than MHs [that would be more, more? for fluorescent?]. That is why I want to explore these new Fluorex bulbs that clearly CLAIM different properties than former Fluorescents. You noticed on the box photos I posted, they CLAIMED 10,000 hours, 6500K, 75% of sun light spectrum, high levels of blue, and very high lumens. As Steve has said Lumens are for people and PAR is for plants, but the CLAIMED wide spectrum should imply good PAR values, although none are given. All the claims may be false, but why ass/u/me they are? So I will be testing. And, as you said, the Fluorex may be more efficient than MH. I am just looking for a lower energy way to provide the light my plants need.

Thanks for the energy analysis [njh and Janet].

Doug, let us know what you find, i'd be surprised if they were more efficient than MH.

They may be the next best thing, and i'd use them if my lighting requirement was less than the minimum available MH wattage, 150W i think.

GD, inefficiencies ARE heat when you're talking about lights. If you're consuming 1KW of electrical energy, and developing 500W of heat, then you're only getting 500W of light. But i do understand that the heat can be used, its just that the other lights have more heat less light.

Doug, good one with the foil!

What are the hardware costs for each of these kinds of lights? When I looked at the home improvement store, I found the MH fixtures hard to find, and then when I found them they were very expensive (I think like over $100?)

The 100 watt Fluorex cost me $49.98 at Home Depot. They have 65 watts for $29.98. The 100 watt bulb costs $9.99 for replacement.

Fluorex definatly sounds cheaper!

for efficiency VS cost they might be the go

Not sure of ticket price of MH, but they are not cheap.

I got my 150W including fixture globe and ballast transformer from the re-cycle yard for about $30, they had a box full, should have picked up more.

Funny, i was just using it now, we were printing up invites, and i fired it up in the lounge room, the colours look much truer under it

Hi Steve,



I agree that heat (where it is not needed) is the thing that makes MH or HPS lights less efficient.

Where, however, that heat becomes useful in the overall context of your growing system design (as it would in the case of our members who live in very cold climates), you improve the efficiency of the light quite dramatically.

Another example......an internal combustion engine is very inefficient because of the amount of energy that is lost in the form of waste heat that has to be got rid of. If you use the waste heat from the engine to provide hot water, however, the engine becomes much more efficient.

See what I mean?

Gary

Gary, heat from electricity here is 3-4 times the cost of heat from natural gas. So for heat, my 30,000 btu radiant gas heater is far better.

My ideal is cold, bright, wide spectrum, hi PAR, great PAR to energy use, and motherhood and apple pie (American expression - might lose something in translation - meaning undeniably good). You are lucky if your days do not get as short as ours.

BTW why don't your days get as short as ours? Or do they further South (Tazmania?)