how to make a mains ac mixer ? - Page 1
Forum section: electronics / projects

author: kripton2035
author_rank: Super Contributor
timestamp: October 01, 2013, 07:07:20 pm
content: hi,I'm wondering how you can do a mains ac mixer.I want to use solar pv cells, but not store energy into batteries.I want to use the solar energy when it's available, so during the day.so,I will "invert" the dc voltage from the solar cells, to a 220 (or 110) ac voltage, that can be synchronized with the grid mains acHow can I mix the grid mains and my solar mains to get a usable mains.I want to use the solar mains prioritary, and if it is not available use the gridHow to do that, to be fully transparent to mains usage and with no mains interruption(i.e. no relay that would switch between the two sources and make a small interruption each time)thanks.

author: Alana
author_rank: Frequent Contributor
timestamp: October 01, 2013, 07:38:13 pm
content: If i would be doing something like this I'd use setup similar to ON-Line UPS with PV in parallel with battery pack. This is the easiest way to ensure that your device would not interfere with mains and for this kind of device [at least for me] it would be a priority.

author: Monkeh
author_rank: Super Contributor
timestamp: October 01, 2013, 07:45:55 pm
content: You would buy a grid-tie inverter. You do not connect anything which feeds power to the grid which isn't properly designed.

author: kripton2035
author_rank: Super Contributor
timestamp: October 01, 2013, 07:58:29 pm
content: Quote from: Monkeh on October 01, 2013, 07:45:55 pmI forgot to say I want something that does not send anything to the grid, only send solar or grid to the houseso it's not a grid-tie inverter ?

author: Monkeh
author_rank: Super Contributor
timestamp: October 01, 2013, 07:59:32 pm
content: Quote from: kripton2035 on October 01, 2013, 07:58:29 pmBest of luck achieving that with no switching time..So, what're you going to do with the power generated by the panels you don't use?

author: kripton2035
author_rank: Super Contributor
timestamp: October 01, 2013, 08:17:53 pm
content: are you forced to use this power even if you don't want to ?if I want to switch off all the lights in my house, I'm not forced to use the power available from the grid ?

author: G7PSK
author_rank: Super Contributor
timestamp: October 01, 2013, 08:20:44 pm
content: You would have to parallel your inverter to the mains after your meter, but I cannot think of any country where it would be legal to just go and do that with equipment that is not approved by the supply company. I would think that any solution that switches seamlessly between the 2 supplies and runs the solar power inverter in parallel would cost far more than a grid tie inverter and in many parts of the world it would pay to send your power to the grid and buy back what you need due to feed in tariffs.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 02, 2013, 03:33:45 am
content: Cheapest way I know of (assuming you don't know how to build a grid tie inverter) is to get an online UPS and connect the panels to the battery through a charge controller.

author: AG6QR
author_rank: Frequent Contributor
timestamp: October 02, 2013, 11:24:21 pm
content: One approach is mechanical. Use a motor-generator. Or in this case, perhaps use two motors to drive a generator that has a flywheel attached. Power one motor with the solar cells, and the other motor with the AC grid. You might use a mechanical clutch or freewheel system to avoid friction losses on an unused motor. By keeping the three electrical systems (grid, solar, and output) isolated electrically but coupled only mechanically, you should be able to get very clean output power. The inertia of the flywheel provides relatively continuous power as you switch from one source to another.But mechanical systems tend to be big, noisy, and maintenance intensive. I doubt this idea is better than a grid tie inverter or UPS, but I don't understand the requirements fully enough to say for certain.