Approaching two years of grid storage operation.

To date we have accumulated about 40,000 kWh stored excess in the grid after almost 2 years of grid connected operation while powering 2 homes. Our local utility has taken about 12,000 kWh of this total to pay for our use of their wires to SEND them the power. They assess DEMAND / DELIVERY charges regardless of which way the power flows. At least they finally stopped taking our $ and are now just taking our stored kWh's to pay the commercial demand / delivery charges. 

Note that Utilities define energy flow to the grid as negative (-) and flow from the grid as positive (+)

So, to the Utility the Net Grid plot here looks upside down, flipped about the 0 axis. 

All the data logger can hold shows the seasonal water availability.

The data logged the last whole month shows the daily use patterns and the waning water as summer drought set in.

Connecting to the Utility Grid

Net Meter Micro Hydro – The Road to Energy Independence

By Robert Honders, Honderosa Valley Consulting

Net metering is the single most effective policy government can implement to promote renewable energy derived from all sources. Why exclude waterpower? If net metering were extended to all small scale (under 25KW) hydro sites, we would see renewed interest in the restoration of thousands of micro hydro sites that have been abandoned during the times of cheap oil. Many of these sites could be made productive again with lower investments because the infrastructure (dam, penstock, water supply) may still be intact. There is no valid reason to treat one renewable energy source any differently than another. We need them all to pave the road to energy independence.

The advantages of a grid connection include energy storage and vastly simplified control of frequency & voltage. Essentially the site runs wide open and just pushes energy into the grid at the grid voltage and frequency. It is analogous to you helping a freight train by pushing on the back of it. You won't be able to change its speed at all, even if your efforts are doubled, or stopped altogether. In other words, your energy input can fluctuate, but the train stabilizes everything just as the grid stabilizes relatively small energy inputs.

The simplest way to get grid-connected and reap these stabilizing benefits is through net metering. Net metering is accomplished using a single-bidirectional meter, which is already in place on all grid-connected homes. But beware! The newer electronic meters are programmed by the utility company to ignore the direction of the energy flow. Thus you can end up paying for the energy that you send to the grid! The power company prevents small energy producers from sharing the energy they generate with their neighbors and turning their own meter backward without permission.         (Older spinning disk meters were not programmable in this way. The worst they could do to you is stand still while you were supplying power, and spin forward as you used power.)

To get grid connected with your hydro powered induction generator (cheapest, robust and most common) you’ll need to use an ‘inter-tie protection relay’ like the Beckwith M-3410. The relay monitors the grid / utility (not your generator) for any type of anomaly, like ‘grid down’, voltage or frequency too low / high etc. If any grid anomaly occurs the relay disconnects your micro hydro output from the grid for their protection. After grid power is restored the relay monitors the grid and if the grid has been normal for 5 minutes it will re-connect your micro hydro. You will need to wire an auxiliary contactor to hang a dump load (space heater will do) on your induction generator while it is disconnected from the grid to prevent your output voltage from rising too high.  Below you’ll find the diagram for a system like this. Double click to enlarge.

Once your utility has inspected and tested your grid inter-tie for proper operation, AND if your state law has hydro power included in the net metering law, then you can ask your utility company to re-program your meter so you can share your excess power with your neighbors and run your meter backwards. Net metering makes it possible to ‘store’ your excess energy in the grid instead of in batteries, and returns energy to you when you need it, perhaps during a dry August, and at the same price.                          

So let’s have NET METERING FOR ALL RENEWABLE ENERGY be the law of the land!

Net Metering, Why not Hydro?

I want to clarify the 'net metering' issue a little. I think that net metering is the most effective policy the government can implement to promote renewable energy derived from other sources besides solar & wind. If net metering were extended to all small scale (under 25KW) hydro sites, we would see a resurgence and interest in restoring thousands of small hydro sites that have been abandoned during the times of cheap oil. Many of these sites could be made productive again with lower investments because the infrastructure (dam, penstock, water supply) may still be intact. There is no valid reason to treat one renewable source any differently than another.

The advantages of a grid connection include vastly simplified control of frequency and voltage. Essentially the site runs wide open without any control and just pushes energy into the grid at the grid voltage and frequency. It is like you helping a freight train by pushing on the back of it. But you won't be able to change its speed at all, even if your efforts are doubled or stopped altogether, in other words, your energy input can fluctuate, but the train stabilizes everything just as the grid does for relatively small energy inputs.

The simplest way to get grid connected and reap these stabilizing benefits is through net metering.

Net metering is accomplished using a single-bidirectional meter, which is already in place on all grid connected homes. The newer electronic meters can be programmed to ignore the direction of the energy flow. Thus you can end up paying for the energy that you send to the grid! That way the power company keeps people from generating energy and turning their meter backward without their permission. ( Remember too, the days when Bell Telephone owned the phone lines and even the phones, and you could not connect your own! They made a ton of money charging a monthly equipment lease fee. So things will change in time with the power grid too.) The power company has to set (program) your meter to distinguish between energy coming or going.

I found this out the hard way when I first fired up our small (12KW) generator, synchronized it to the utility power line (grid), connected through a circuit breaker, opened up the butterfly valve controlling the power output and started really pushing that train. Then I sauntered out to the (electronic) meter on the pole and lo and behold the reading was increasing at a rapid rate! I could not believe that I was being charged for the power that I sent to them.

So now what can I do? Yes, I can get grid connected but only through an expensive switch which they have to approve. ( Remember Bell Telephones "approved communications interface"? ) And until I satisfy these interface switch gear requirements they won't reprogram my meter. They claim safety issues, (as Bell Telephone did up to the late '70's) But this is a red herring. If the grid goes down, (the train stops) there is no way that my 25KW is going to keep pushing that train ahead, and if it tries, any ordinary circuit breaker will disconnect me from the grid. The net metering of solar and wind energy requires little in the way of special disconnects either so why should renewable water power be any different?

So join me and lets have NET METERING FOR ALL RENEWABLE ENERGY be the law of the land! And while we are at it we should demand a favorable feed-in tariff for all renewables as well. More on that later.

SIZING UP YOUR STREAM FOR HYDRO POWER

The huge variation in stream flows during a season make exact measurements difficult and un-necessary. We experience 500 to 1 in a typical season, and I have seen 5000 X more water than typical low flows. An existing dam, batter board wier or even a place in the stream where all the water is flowing through a fairly constant depth channel or puddle will do to make observations and measurements that are detailed below. I think a computerized data logging setup is ideal but over kill. It is also likely to go down stream in the first big storm. And if you are lucky enough to experience a 100 year event you'll not only lose your equipment and maybe your dam, but you will see first hand what your intake structure has to be built to withstand! And yes, that wooden flume is temporary / test. It will be upgraded to stone (for aesthetics) and concrete for strength and durability. Look at the live webcam on the intake
http://powershack.shacknet.nu:1026/


Why measure something that varies sooo much so exactly? Any experienced hydrologist or keen long time observer of a stream can tell you the 'design flow' to use for your micro hydro setup. A hydrologist or you could determine the watershed area by studying Google earth. The watershed area and the number and size of the lakes and reservoirs tells you a lot about your stream or river. Our watershed is only 1.5 square miles and contains only one 2 acre pond. Our rainfall data shows about 50 inches / year, another figure to add into your considerations. Then you should try to determine (by a few measurements throughout a year) 'Q95' , the Quantity of water flow that is exceeded 95% of the time. So only 5% of the time there is less water and you won't be able to run your system effectively and leave enough water for the fish.

Another useful figure to estimate is 'Q50' , the quantity of water exceeded half the time throughout a year. This is the upper limit on your design flow and you will tend to spend more on bigger pipe and turbine, run for only half the year (on average) but produce the most KWhrs. This design flow should only be considered if you are grid connected and selling back. I selected Q75 (1800 Gal/min in our case) for our design flow because we run autonomous (totally off the grid) for 9 months when we have plenty of water to make about 20Kw 24/7, all of which we try to use up in 2 1/2 households.

We switch back to the local utility for a few months in the late summer when we don't use much electricity anyway, and don't have enough water to keep Q95 (150 Gal/min) flowing. My ultimate goal is to work out an arrangement with the utility company to become grid connected. Then we could 'store' the winter generated excess power in the grid and withdraw this 'stored' energy during late summer. Ideally the Utility would allow us to 'net meter' like they allow for wind, solar, and bio generated electricity. Net metering does not require any special equipment or meters, the energy flows both ways, and your existing meter runs forward and backward to keep track. But alas, the Utility in their infinite wisdom, excludes Micro Hydro from net metering. So we should all lobby to get net metering for all renewable energy. Even a cap, of say 25 KW, would be acceptable. Beyond 25 KW you could probably justify the expenses of special meters and switch gear. Now I'm Getting off topic.

Happy Hydro!
Rob