Isn't 140'F the hash-mark on the thermostat?
Nobody showed you a circuit before because you didn't give enough about the system.
Battery / No Battery are VERY different animals.
With a battery, 2 tanks, and a dump load...
(I am trying not to sound like a product commercial, but this is what I know a lot about)
I would use 3 of my controller circuits. A circuit link follows, but read this first.
The 1st one set as an LVD, but with a higher voltage and less hysteresis, feeding the first tank.
The second one just the same, but the voltage and hysteresis a bit higher.
The 3rd one feeding a dump load large enough to handle everything the windmill can make, and a bit more.
Tha factory thermostat contacts are in between the "output to power fet gates" and the gates.
If the battery is high enough to suit controller #1, it sends a signal to thermostat #1. If the water is cold the thermostat is closed so the power control device (power fet) turns on the heating element. Tank #1 heats water.
When the battery is a bit higher, and high enough to suit controller #2, it sends a signal to thermostat #2. If the water is cold the thermostat is closed so the power control device turns on the heating element. Tank #2 heats water.
If the battery is in danger of overcharging, controller #3 sends power to a dump load.
Depends on the loads, but the power fets may require minor changing of the circuit.
Or the power fets might be better replaced with IGBTs.
Your math, going from 50'F to 130'F in a day, without any losses... Might not be worth the second (or is it the 3rd?) tank and the related costs?
If it is windy, then it is winter (you said it). Heat is good in winter.
The flip side... In summer, not much wind and don't need the heat. But the 2nd (3rd?) tank would act as a tempering tank to get the water to room temp without any electricity cost.
http://www.fieldlines.com/story/2007/8/24/172521/889
Forget about relays.
High tech transportation in Florida...
Was a horse, 400 years ago.
Was the Space Shuttle, 25 years ago.
Relays are closer to the middle than most people think.
Windmill "Wild AC" to a heating load is an expensive complex nightmare, best I can tell.
Are you confused more or glad you asked?
G-