Posts tagged with "solar"

Mi-Grid vs. the Powerwall

We’ve had a lot of requests to layout the difference between a Mi-Grid system and a Powerwall. So, here goes!

First, let’s define a “Powerwall”. It is a Lithium-ion battery pack. It is not a complete power system. Implementing it requires a StorEdge inverter from Solar Edge. If you have solar, you also need a SolarEdge grid tied inverter and all of the required safety systems, breakers, disconnects, to properly implement. The “cost” most people associate with the Powerwall is only the price of the battery pack.

The SolarEdge+Powerwall system is a Grid-Tied solution. It cannot be used for off-grid. The Powerwall+SolarStor is designed to supply short term power from its battery pack for short (hours) service interruptions. If solar is present, it can store and disperse energy from the solar panels after sunset. However, the cost to store and retrieve the energy may be above the cost to sell to the network, even without net-metering.

Mi-Grid was originally designed as an Off-Grid system, specifically for the Off-Shore oil industry. It is designed to allow long term or permanent power with or without a utility connection. Mi-Grid’s Energy Management System (EMS) can take in multiple AC and DC sources, supply power and recharge batteries, all at the same time. It is also rugged and can be implemented outdoors.

Mi-Grid is “Agnostic” with respect to AC power, type of and manufacturer of solar panels, battery systems, as long as they meet the specified voltage ranges. Mi-Grid even has modules which can make use of “dirty” unstable utility power and turn it into “clean” pure sine-wave power.

Mi-Grid can be connected to a generator, allowing off-grid or utility down operation. The generator is only used off-grid or if the utility is down. The Generator recharges the batteries on cloudy or high power usage days, then shuts down. Even when operating with the generator, the solar array can assist recharging the batteries and supplying power. If the batteries become full, the EMS will modulate the array to match the power required,

The StorEdge-Powerwall system cannot implement a generator safely, unless the entire Solar/PowerWall/Stor-Edge system is bypassed. It uses a grid-tied inverter which cannot modulate the solar array output. Once the batteries are full, if the solar array output exceeds the user’s needs, it would send power to the generator, probably damaging it, potentially catastrophically.

Cost: It depends. Don’t you hate it when people say that? Mi-Grid comes with a generator and many more AC and DC inputs. If you eliminate the generator, you can compare the costs of the systems. The most fair comparison would be a Mi-Grid 1000 or Mi-Grid 2000 setup in essential circuits configuration. A Mi-Grid 1000 costs around $28,000 installed with 4.7kW solar and a 10kW generator. A Mi-Grid 2000 costs around $47,000 installed with 9.4kW solar and a 16kW Generator. Depending on location and codes, these prices can vary. For a “fair” comparison, you would need to implement 2 Powerwalls with any StorEdge System. You also need to include a SolarEdge 5 or 8kW grid-tied inverter and Optimizers at each panel.

Capability Comparison

Mi-Grid 1000 Mi-Grid 2000 SE5000+PW SE6000+PW
Max AC Power 4000 8000 5000 6000 Watts
Max AC Surge 8000 16000 7300 7300 Watts
Maximum Battery Output 4000 8000 1xPW=3300, 2xPW=6600 Watts
Energy Storage 19.2 38.4 1xPW=6.8, 2xPW=12.8 kWh
Energy Storage Usable 9.6-15.4 19.2-30.8 1xPW=6.8, 2xPW=12.8 kWh
Noise <30dB <30dB 1xPW=56dB, 2xPW=61dB  dB
Generator for contingencies Yes Yes No No
Grid-Tied Yes Yes Yes Yes
Off-Grid Yes Yes No No
Sell Excess Power Yes Yes Yes Yes
Run Whole House Air Conditioner No Yes No Maybe
Battery Life 3000 or 1800 Cycles,

50%/80% DOD respectively

1000@20% capacity loss

3000@60% capacity loss

Outdoor Rating NEMA 4/IP66 StorEdge IP65, PW IP10


Getting ready for a Hurricane – from Mi-Grid

I live in the Gulf Coast area and hurricane preparedness is extremely important. About every 10 years, my area is hit with a hurricane, tropical storm or other disasters. It is much more important to prepare ahead, than wait until the announcement by the weather forecasters.

Run or Hide?

The saying is run from the water, hide from the wind. It means if your area will flood, get out of there! If your area won’t flood, you can “hunker down”, protect yourself and generally stay in your area.

Run from the water. Flooding is no joke. There isn’t anything you can do except evacuate. If you are in a flood-prone area, your preparedness is to have an inland location in mind, and your irreplaceable items “ready” to go. Know your evacuation route. Consider side roads and county roads which the rest of the public are not familiar. Keep extra fuel handy since there is usually a run on fuel just before the storm. Be prepared with a few days of food and water, since it may take time to evacuate. Remember, there will be LOTS of other people, so it will take much more time to get out of your area than normal.

Hide from the wind. Most people should stay where they are. First, the roads will be clogged with the people who need to evacuate. People in areas which won’t flood do not need to leave. If they do, they make the evacuation routes worse. So stay if you are not in a flood-prone area.

What do you need if you will be in a place to stay?

Food, water, and shelter. Your house is generally enough for shelter. If you are inland, the winds may be strong, but they generally not high enough to destroy your house. Most serious damage is storm surge and flooding. You may consider boarding up windows. Focus on the south and east windows, as this is usually where the wind comes from. Also look around your yard and remove anything which the wind can move. If you have a pool, tables and chairs can go in the water.

Food and water. Most people think they need bottled water. The water that comes out of your tap is EXCELLENT. But the power may be out and the water pumps off. So store water. How? Trash cans. Buy new ones!!! And you might want to put line them with trash bags. You also want to fill bathtubs and have a small bucket for pouring into toilets for flushing. Just buy the trash cans early and store them away unused.

Food you have a lot of choices if you prepare ahead. You can buy survival food. Not super tasty, but it is better than nothing. You can buy canned food. If anything needs heat to prepare, make sure you have a portable stove and fuel. Have a minimum of 2 weeks of food for every person in the house. That is about how long it will take to get emergency systems in place!

One real issue is post hurricane. In many places, the power may be out for weeks. Many people use generators to help them through. Portable generators need fuel and long-term storage of enough liquid fuel for 2 weeks can be a problem. They are loud!

Permanently installed natural gas or propane generators are much better. They have a big fuel source and they are not as noisy as portable units. They do require maintenance, so be prepared to change oil and spark plugs every 100 hours or every 4 days!

The best solution is a hybrid solar system combining solar panels, energy storage and a generator. It provides the power you need with minimal use of the generator. And the solar panels will save you money the rest of the time!

For help with hurricane preparedness, contact Tetra West Technology and ask about a Mi-Grid!

Save the world from Cow Farts!

Well, maybe solar can’t stop all greenhouse gasses. Renewable energy comes from all sorts of places. Landfills, cow manure and other places with organic decomposition produce methane, along with other gasses. Here’s an article about how California is trying to rid the world of these nasty gasses. Methane does have a much higher greenhouse effect than carbon dioxide.

OK, everyone raise their hands that tried to light a, uh, well, forget I brought it up. Let’s just say that, those gasses, can be flammable!

These “organic gasses” can be used to produce electricity. A gas turbine, basically a jet engine that sits on the ground, or a big reciprocating engine, like a car that doesn’t move, can take that explosive gas and burn it and turn a generator to make electricity. And if there isn’t enough hot air in the world, the hot exhaust from these engines can be used to make hot water or steam.

How exactly do you go from, well, bull crap to high value fuel? Very carefully! Click-on the illustration below


It’s a dirty job and someone has to do it! And even better, Mi-Grid’s generator can run on these gasses! (Had to tie Mi-Grid in SOMEHOW!). See how a Mi-Grid can help you keep the lights while saving you money!