Just wondering... who will be doing the sparky work for you, if you're not familiar with it?
I don't suppose many people here actually pay much attention to it, but the government has mandated that all but the most simple electrical work be notified to and possibly inspected by building control officers from the Council. Even 12V DC lighting in your garden that isn't composed of "pre-wired sets" (i.e. you don't do any wiring connections other than plugging the thing's mains transformer into a socket) is supposed to be "notifiable work" that must be done by a "competent person" (paid electrician).
Next they'll demand that you need a man in a hazmat suit and goggles to change your bedside table light bulbs
But on the other hand, big batteries, wind turbines, heaters and power electronics are dangerous things to be playing with. Each has the possibility of catching fire, blowing up, or causing chemical burns.
Unloading a turbine at full power can result in a very dangerous over-speed that will destroy the turbine and send high speed mechanical wreckage travelling for quite some distance (one of Frotter's missing turbine blades was discovered on a neighbouring cow shed
). Over charging a battery will result in explosive hydrogen gas or even thermal runaway in the battery that can boil the acid and cause an explosion with acid burns.
Unless you know
exactly what you are doing and understand the risks (including the risk of having your buildings insurance invalidated in the event of a disaster involving your experimental power project and being prosecuted by the Part P police), then don't do anything.
Probably the only "legitimate" way to do what you want to do is to get an MCS accredited electrical company to install the turbine as a grid tied generator and then just run a 230V AC immersion heater as installed by a registered electrician. If you pay an industrial control electrician a few thousand more Pounds, he might rig up an "approved" method of sensing the power output of your turbine and driving a simple on/off relay to limit the amount of power the heater draws from the grid rather than from your turbine. Anything else gets you into hot water (or astronomical expense) as you are then in the realm of commissioning a new design that will have to under go safety testing to meet a plethora of standards.
Try talking to your local building control officer about commissioning a custom designed, home made PWM power controller for a wind turbine powered immersion heater and they won't have a clue, but the stock answer will be, "No, you can't do that. There's no standard for it. The computer says no". They mostly just rubber stamp notifications for having a light bulb installed in your kitchen ceiling and then collect their fee. They will then demand a full "drains up" study to be commissioned into the risk analysis of your design and hire some engineering consultants at £2000 per day at your expense "to look into it"... Before demanding a load of tests and certifications (at your expense again) to get the thing approved as a "one-off". Assuming you've got thousands of Pounds and months of time to waste on all that red tape, you might be allowed to use your invention to save a few quid on your water heating bills.
Meanwhile, back at the illegal DC wiring installation at your home...
If you use a Morningstar Tristar PWM dump load controller on the batteries, they won't get discharged at all. They will get full and then the PWM charge controller will dump the precise excess energy into your heater element. When the wind stops, the battery Voltage will fall below the float fully charged level and charge controller will just stop sending power to the heater. It will almost infinitely vary the power to the load from zero to the full 1000W that the heater can draw. If your turbine can put out 1.6kW in a storm, you'll need some fail-safe brake relay or another dump load and controller to protect the turbine from over spin.
You just need to make sure the controller is properly rated for the dump load. 1000W at 48V is only 20 Amps, so the 45 Amp controller will do. If you go for 24V turbine, then the current to the load will double and you'd best go for the bigger 60 Amp controller.
You need to limit the charge current from the turbine to the batteries to C/5 (or about 20A per 100Ah battery). More than that and the battery will heat up and make lots of gas.
If you just want to use the power for heating and aren't interested in using the batteries, you could replace the batteries with super capacitors, as these will charge up almost immediately and just provide the short term energy store that the charge controller needs so it can work to maintain a constant Voltage across it. Super capacitors where used in the TV show that had 90 bicycle generators connected to Tristar controllers and to an off-grid inverter to run a test house for a day. The super capacitors gave the folk on the bikes a few seconds of buffering in power demand, so that they could watch a big meter and speed up pedalling or add more riders to meet the demand. Super capacitors also have very high charge efficiency, so the riders didn't waste precious energy on charging losses for normal lead batteries. Super capacitors are expensive beasties though, so a bunch of small batteries can achieve much the same thing.
