Mini-Series Part 4: Why You Should Consider Adding Batteries to Your Solar System

Welcome to our Solar Mini-Series. Our Mini-Series will try to answer questions about solar that homeowners may have. This final video discusses the purchasing considerations for solar power. A full transcript of this video is found below the video. Feel free to check out the other videos in our Solar Mini-Series.  

Full Transcript: In this solar mini class, we will consider the benefits of including an energy storage system as part of your renewable energy system. For most systems the cost to make your own energy is around five cents per kilowatt hour. For a utility to generate energy from a large-scale solar array is around four cents per kilowatt hour. Net metering programs have helped solar to grow in the United States by allowing owners to pay for their systems in four to five years, after which the next 20 plus years of energy bring a great return on investment paying more for energy than it costs them to generate it themselves. This has caused the utilities concern because it is not a sustainable model for them. This has resulted in a number of rate changes and additional fees being imposed on owners of renewable energy systems. Let’s talk about another reason Solar causes the utilities heartburn. This graph shows the typical energy supply for a utility base load generation. This is what the utility needs to supply 24 hours a day seven days a week and is usually provided by coal oil and nuclear generating facilities which are expensive assets with a long return time on investment and cannot easily change the amount of energy they produce. Intermediate generation is provided by spinning reserves and purchases from other utilities on-the-spot energy market. Load following and peaking are generally provided by gas fire generators or diesel generators. With renewables like hydro wind geothermal and solar fitting in where they are available, perhaps the most talked-about problem with solar energy is the duct curve the issue of solar providing its maximum output at a time that does not easily meet the load profile. Experienced either by the homeowner or the utility notice how the load curve is pushed lower and lower as more solar production is added to the grid. Leaving the utility with the choice to turn off expensive assets that are difficult to restart try and sell the excess energy to another utility who needs it for the moment or the most common choice which is to curtail the renewable energy production. This is the easiest solution, but then the benefits of the renewable energy, which is cheap fuel, is lost. Here is the solar production curve in green and a typical home energy use curve in blue. Most homes have a peak in the morning and a bigger peak in the evening. As you can see, the main portion of a home’s usage falls outside the solar production window. This is where the deepening belly of the duct curve comes from as production exceeds demand during the solar production window. The following graphs will help illustrate the problem in adding renewables to the grid in areas of the U.S. Solar energy has reached a five to ten percent penetration in the energy mix. It seems small and we wonder why it would cause the utilities such problems, but unlike other generation assets, renewables are not available 24 hours a day, unless they include storage. Currently, 95% of new solar installations are grid interactive only. This graph shows a contribution of 5% to the energy mix from solar generation looked at over 24 hours. In reality, we see that a 5% energy contribution from solar without storage actually provides 30% of generation during the main solar production hours and nothing outside that window. A 10% contribution of solar without energy storage provides 55% of generation during the peak of the day, which pushes into base load generation and forces the utility to ramp down or turn off other generation elements and sell the extra energy on the spot market if possible. The other option is curtailment. This is where the renewable generation is turned off or throttled down, which is much easier for the utility to do but then the benefits of the renewable generation are lost. So how do we fix this problem? This is the same energy curve we looked at before only with energy storage added to the home. Notice that the extra energy is now stored during the solar production window; instead of being sold back to the utility and time shifted for use during the homes high use times. The utilities like this energy shift from the batteries as it allows your home to appear to them as net zero, in other words no effect since they need to predict with some accuracy the load profile for their system to operate as efficiently as possible. Time shifting of the energy production does not equate to battery backup, unless the renewable energy system includes a smart inverter which can isolate the home from the grid during an outage forming its own micro grid. The top two pictures show systems with lead acid and nickel-iron batteries. Notice the size special containment and venting requirements. The bottom pictures show systems with new battery technology. Notice the size difference of these systems. They do not require special containment venting or security. Making and using your own energy connects you to the environment much as our ancestors were. When the Sun was shining they did laundry and when it was cloudy or rainy they waited for a sunny day. With a solar plus energy storage system you will be more mindful of how much energy you are producing and how much you are using. Often, upgrades for energy efficiency are part of a total solar system installation allowing a smaller system and reducing costs. Knowing how your home uses energy provides valuable information. We believe that system energy monitoring will be part of solar powers systems moving forward. At the beginning of the solar revolution, the grid was able to accept the power generated from renewables with little effect. At the levels now being added to the grid, the utilities face major changes to their infrastructure, rate schedules, asset management, and future planning. Most utilities are not opposed to renewable energy. What they want to do is slow down its adoption to a rate that allows for better long-term planning and control. For the energy market, solar is a disruptive technology. It gives customers choices never before available and forces dramatic changes in the way utilities plan and operate storage systems. It provides a number of benefits to the utilities in addition to the homeowners, even if they are not coupled with renewable energy sources like solar or wind. Batteries have been the weak link in storage systems. with the best and least expensive options being the lead-acid related technologies, which have not changed much since their invention over a hundred years ago. The industry is now seeing increased research and development with breakthroughs in battery technology, largely driven by the desire for longer life in cell phones, laptops, and other personal electronics. The solar industry has benefited from this research and along with electric vehicles. They have helped to increase the demand for better battery storage options; this is something that we’ll look at in a future solar mini class. I hope you will join me then. Thank you.

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