Are you prepared for the costs of cooling this large of a grow?
500kW of light means a lot of heat. 100 tons was mentioned earlier. And I would like to mention why that is way off.
500kW of light means somewhere in the neighborhood of 500kW of heat. Add the heat from ballasts and you are looking at nearly 600kW of heat. Best to be on the safe side and assume 200W of heat to the ballast. I've seen some that put out 175W of heat, and some as low as 100W. This is a ballast efficiency thing. They range from 94% on the high side down to 80% of the low side. But, good luck getting good data sheets on most of these ballasts to tell you what it really is. Anyway, 600kW of heat.
1w = 3.412 btu/hr.
600kW of heat = 2,047,200BTU/h.
12,000BTU/hr = 1 ton of cooling.
2,047,200BTU/h = 170.6 tons.
Add the heat of the summer to that as well as the rest of the building. +20 tons maybe. Depends on the insulating characteristics of the building. +10 tons at a minimum.
Add redundancy to that. Do you really want your cooling system to suddenly be way undersized in the event of a failure? 88F and 90% relative humidity is a very bad thing for the plants. 77F and 40% RH is a reasonable temperature to run. We are talking about a very valuable crop here. Redundancy in very important. +25% at a minimum.
As high as 225 tons of cooling.
Most general contractors you talk to will say ~$2500/ton installed. $575K is a possibility.