Author Topic: Direct heating (Read 2011 times)

Seedler · « **on:** March 11, 2007, 02:10:40 PM »

Hello all,

I recently purchased a 3kw grid tie wind system. 3kw 3 phase turbine, wb3000 windyboy inverter and 3kw dump heating load. I am in UK so my grid voltage is 230v 50Mhz. The turbine has no furling tail system, I think it is just diverted to heaters or short circuited in high winds.

Anyway my problem is this: The controller was lost in transit. I am getting a replacement but it may take a while. I was wondering if there was anyway in the mean time to connect it to the divert load supplied or another type of heater(say immersion)just so I can get it up and doing something.

Would directly connecting the turbine to the heater damage it in any way? And how do you connect a 3 phase output to a heater?

Any help would be appreciated.

Dee.

jimjjnn · « **Reply #1 on:** March 11, 2007, 09:04:09 AM »

2 Single phase heaters?

vawtman · « **Reply #2 on:** March 11, 2007, 09:09:52 AM »

Is it new with a warranty?

Do you guys need a permit over there to gridtie?

You may be able to rectify to dc and feed the element that instead of 3 elements.I think.

How much was the inverter?

Seedler · « **Reply #3 on:** March 11, 2007, 09:49:11 AM »

Yeah I do have a warranty. I suppose connecting it directly to heater would void it. But if its safe to do so I would consider it.

You do have to get a connection agreement over here for connecting to the grid, but its a simple case of letting them know when you want to connect and what grid inverter your using.

I got the 3kw grid tie windy boy inverter for £1400 from "Wind and Sun" that would be around $2600.

Dee.

Nando · « **Reply #4 on:** March 11, 2007, 12:53:05 PM »

Dee:

Can you detail all the parts of your system and the specifications ?.

The wind mill can not have a full load resistor "attached" to the generator because it represents a stalling load.

The load the wind mill can accept is defined by the power available in the wind and the mill area.

To use the wind mill as heating source you need a variable load controller to keep the wind mill RPM at is peak power level, for proper energy harvesting.

Nando

vawtman · « **Reply #5 on:** March 11, 2007, 01:57:56 PM »

Nando wouldnt a heating element be considered a variable load controller?Has the power available in the wind increases the element gets hotter up to its rating.I know im probably wrong but why?

RP · « **Reply #6 on:** March 11, 2007, 05:07:12 PM »

I think the problem is that the heater provides an almost fixed resistance. This is fine at the high end of power since as you say it simply gets hotter and dissipates more energy as heat.

Unfortunately at the low end it'll likely be too much of a load and prevent the thing from ever getting out of stall and/or make it really slow to start up.

Seedler · « **Reply #7 on:** March 11, 2007, 05:41:14 PM »

The turbine is 3 phase 3 wire. I'm pretty sure it has a voltage range from about 250 to 500v ac.

Dee

Nando · « **Reply #8 on:** March 12, 2007, 08:53:14 AM »

A fixed load to a wind mill is a fixed load and if the load is designed to "load" the wind mill at is peak power then the low resistance value of the load will present a stalling load to the wind mill.

So at every wind velocity point the generator produces a wattage that can not be increased so the load needs to be varied to just HARVEST such watts at that moment.

Nando

Nando · « **Reply #9 on:** March 12, 2007, 01:18:17 PM »

Dee:

What is the generator voltage, can you describe the Volts /RPM ?.

What, exactly do you have available, besides the wind mill & generator ?.

What was lost ?.

If you have a ballast dump load, what is the resistance value. ?.

When do you expect to have the replacement parts that were lost ?.

Nando

Seedler · « **Reply #10 on:** March 13, 2007, 04:18:40 AM »

Nando,

The voltage range of the turbine is 192 - 500v. nominal voltage is 240v ac. The rated power is 3kw with a max of 4kw.

I have everything except the grid tie controller. I have the turbine, blades, tail, tower wiring meters, 3kw dump load heater, and grid tie inverter.

The dump load has 3 wires going into it. If I connect any 2 together I get a resistance of 240 ohms. If I connect all 3 in series I get a reading of 180 ohms.

At the moment I'm still fighting with the shipping company to replace the controller so it could take a few months before I get a new one.

Dee.

(unknown) · « **Reply #11 on:** March 13, 2007, 05:36:17 AM »

Wait.

The resistance of heating load is fixed. The load is a function of voltage and current. Now when your turbine starts the RPM are low and the voltage is low. The low voltage creates the low current and it means that the load is low.In other words - if the RPMs of your turbine increase the load created by fixed value heating resistor increase too. 3kW load is of heating resistor (resistors) is at nominal conditions - at nominal voltage. If the voltage is not 230V but 100V the heating load is not 3kW but approx. 560W. No stalling in case of permanent connected load.

Simply the law of Ohm: P=U*I=I^2R

If P=3kW, U=230V Then R=17.7Ohm ( At 230V and 3kW I=P/U=3000/230=13A)

At U=230V P=13^2*17.7=3000W (approx)

At U=100V I=U/R=100/17.7=5.65A and P=U*I=100*5.65=565W

Flux · « **Reply #12 on:** March 13, 2007, 09:16:39 AM »

This has been so vague as to make no sense until now. I think I have finally worked out what you have.

It seems as though your machine is intended for grid tie with the windy boy inverter but the dump controller is a backup to hold the volts down to a safe level for the inverter, it will not normally be in operation but in high winds it will clip the peak voltage to prevent damage to the inverter.

I have no idea if your dump load is capable of dissipating the full power of the turbine, I suspect not, what would be the point if the intention is to feed power to the grid.

You may find that the resistors and just slammed in as a peak limiter with the intention of driving the blades into stall to hold the peak level within range of the inverter.

Unless you find out for sure how this is all intended to operate then You are on tricky ground.

I suspect that under normal conditions you could run the inverter but you would have to watch it in high wind and with no furling you may get out of control.

You will not hurt the turbine to run it for heating but you may wreck your dump load if it wasn't designed for that.

With this new equipment and your seemingly total lack of knowledge of what you have, I think you would be foolish to mess about with the dump load. If you have enough knowledge you could build a controller for water heating using immersion heaters, but if you have that knowledge you could probably build a voltage clipper for the inverter, but having spent money on one that seems crazy.

Flux

vawtman · « **Reply #13 on:** March 13, 2007, 04:46:57 PM »

RP but what if one added caps rated for the full load?I guess like what Zubblys doing and from last i heard having success.Mini batteries if you will.

RP · « **Reply #14 on:** March 13, 2007, 08:47:33 PM »

Yes, capacitors can work but not as anything like a battery. By placing an appropriate capacitance in series with the resistance heaters, the load can be essentially zero (very high effective total resistance, impedance actually) at very low rpms and low at high rpms since the capacitors will essentially conduct more power at higher frequencies.

Generally the capacitors have to be pretty big though.

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