Study Finds the Storage of Solar Power Increases Consumption and Emissions
Recent research from the University of Texas at Austin suggests that the greatest environmental and economic benefits from solar power come from sending excess solar power to the utility grid instead of storing it on-site for later use.
The paper examines the costs and benefits of adding energy storage to homes with existing solar panel systems. While the number of American households with rooftop solar panel installations has rapidly reached the level of 1 million, many fewer homes have a means for storing any excess solar power that is produced. However, there is a growing interest in the on-site storage of excess solar energy, and this study sheds some light on the factors involved in this decision.
Solar Power Still Effective Without Storage
The main thrust of the paper’s findings is that there is no need to have a storage system in place to benefit from the installation of solar panels. One of the most common negative myths about solar energy is that it requires the installation of an additional storage system for when the sun is not providing adequate electricity. However, it is actually more efficient to merely switch to grid energy during times when solar is inadequate rather than storing excess solar power.
The researchers found that the storage of solar power for nighttime use will actually increase a household’s energy consumption, compared to the use of solar panels without any form of storage, due to the consumption of additional energy caused by the charging and discharging of the storage unit. While an increase in energy consumption as a result of storage is not surprising, the level, from 8% to 14% over the span of one year, was much higher than anticipated.
Storage of Solar Power Leads to Greater Environmental Impact
The study discovered that the addition of storage indirectly increased overall emissions of carbon dioxide, nitrogen dioxide and sulfur dioxide. The increased emissions are due to the increased energy consumption that is required to compensate for the inefficiency of household storage. However, since storage will affect the time of day that a household will draw electricity from the grid, it will also reduce emissions in that way.
The benefit for utility companies is more clear. The storage of solar energy reduced peak grid demand by 8% to 32%, as well as the magnitude of solar power fed into the grid by 5% to 42%, which is beneficial for the utility as it will reduce the amount of required capacity.
Overall the analysis demonstrated that the storage of solar power now offers less environmental benefits than sending it into the grid, since the energy that is lost to inefficient storage will ultimately be covered by electricity from the grid that is produced using a high proportion of fossil-fuels.
It’s easy to imagine your clock, cell phone, or cordless screwdriver running on a battery, but how about your whole house? Elon Musk’s innovative company Tesla Motors, maker of the popular line of electric vehicles, announced recently, that it will begin production on such a whole-home battery within the next six months.
Imagine being able to store power, such as the energy gathered by a rooftop solar system or a wind turbine, and store it until needed–or even sell it back to the grid, via reverse metering. No more worries about ever-mounting utility costs or power loss due to inclement weather; the feeling of independence and the comfort of acting responsibly about the environment would be enjoyable, as well. These batteries might make that dream of freedom a reality.
Tesla’s plan is ambitious and optimistic, but what challenges might the company face in actually bringing these batteries to market? Well, the obvious one is price–batteries are extremely expensive, as anyone who has fretted over the cost of even a pack of AAs knows. And batteries that could power an entire house would not only be expensive, they would be very large and heavy (a sizable part of the weight of an electric vehicle is simply from its battery).
Because of their size and expense, these home batteries are not something that you would want to replace on a regular basis, so they would need to be reliable enough to last for years, charging and discharging on a regular basis. Even power companies–who could use large batteries to store excess energy produced during less-demanding hours in order to bolster supply during peak times–are only deploying them in a limited and somewhat experimental way, so far.
If even utilities are a bit leery of adopting batteries on a grand scale, how readily could they become staples in a residential neighborhood? Tesla understands it might be slow going for a while, but the company is determined to keep pushing inexorably toward a greener future.
Besides being Tesla’s CEO, Elon Musk also chairs the board of Solar City, a company that provides solar power systems for homes and businesses. He can see that more and more homeowners are adopting solar systems, especially as the price has steadily dropped over the past few years. Batteries that store the solar-produced power and discharge it when needed make perfect sense with this type of system, since the sun doesn’t shine all the time. The inevitable growth in demand for the batteries should lower costs, just as it has done with the systems themselves. Whereas before, most of us suburbanites could only dream of powering our homes with sunshine, it’s becoming more and more within our grasp.
Another way Tesla plans to reduce cost to individual consumers is by mass production. Tesla’s “Gigafactory”, currently under construction near Reno, Nevada, will be the world’s largest battery factory, enabling Tesla to help alleviate cost concerns by having the ability to produce the batteries in large quantities. As for any concerns as to reliability, Tesla’s years of deploying the lithium-ion technology in its car batteries has provided a good track record.
Many other companies are poised on the brink of jumping into the storage-battery game and will be watching Tesla’s every innovative move. Even if not all the power is yet produced by clean sources, the use of batteries will still help curb the overproduction of power by the non-clean ones, and that’s a win by any reckoning.
The Department of Energy has published a new tool to inform consumers of the financial benefits of switching from a gas vehicle to an electric vehicle. The new tool called ‘eGallon’ compares the fuel cost of driving an electric vehicle vs. the fuel cost of driving a gas vehicle. The results make it appear that anyone who is still driving a gas vehicle must be a complete financial idiot. The problem is, the calculations are incomplete and misleading.
The calculations show that fueling an electric vehicle has a cost equivalent of paying $1.14 per gallon of gasoline. That’s a national average. Results differ by state. According to the government, this makes the fuel cost of electric vehicles about one-third that of gasoline.
The calculations are based on an assumption that the average 2012 model automobile has a fuel efficiency of 28.2 miles per gallon of gas. Starting with this number, it’s then a matter of calculating how much electricity would be required to drive the average electric vehicle that same distance then calculating the cost of that electricity. The result is the eGallon value. So far, so good.
Because both electricity rates and gas prices can vary quite a bit from state to state, the tool breaks down the eGallon cost by state. In Texas, for example, the average gallon of gas costs $3.37 as of 6/10/2013. The eGallon rate is $1.09. In New York the spread between the gas rate and the eGallon rate is smaller. Gas costs on average $3.70 while the eGallon rate is $1.80.
But here’s the problem
The eGallon tool, while interesting, is still only a very rough approximation of the true savings any given consumer might expect as a result of going electric. And it ignores some important facts which make its ultimate conclusions somewhat questionable.
For starters, it doesn’t take into account battery costs. The batteries required to make electric vehicles work aren’t found in gas vehicles. They are very expensive, and have a finite lifespan before they must be replaced. This replacement cost should be factored into the fuel cost for an electric vehicle.
If we assume, for example, a replacement cost of $7,000 for the EV battery and a lifespan of 100,000 miles for the battery it adds about $1.97 per gallon to the eGallon rate (7 cents per mile x 28.2 miles per gallon). It turns out that electricity cost isn’t even the primary factor in the fuel cost of an electric vehicle. That’s a pretty significant omission in the government’s eGallon calculation.
A large amount of the cost of each gallon of gas is made up of federal and state taxes levied on each gallon of fuel. The amount varies but in Texas it is around 38 cents per gallon. It can be as high as 69 cents per gallon in places like New York. A very large portion of these taxes go to pay for things like highways and bridges.
The money needed to keep roads in usable condition must come from somewhere. If the entire country magically switched to electric vehicles today we would have to come up with the equivalent of around 40 cents per gallon of money from somewhere to pay for the roads and other public obligations.
In other words, at a macro level we aren’t avoiding 40 cents per gallon of cost by not buying gas for our cars. We are just shifting that cost somewhere else. It will ultimately come back to us in the form of another tax. This is precisely why some states have toyed with the idea of a tax on electric vehicles.
One could reasonably argue that when comparing the “per gallon” cost of gas vs. electric, the tax amount should be removed from the equation. This money does not represent a fuel cost. Wear and tear still happens to the roads regardless of how the car is powered. That cost doesn’t disappear because we stop buying gas. It just gets shifted somewhere else.
For the sake of a proper comparison, you can either remove the taxes from the cost of the gallon of gas or you can add it to the eGallon. Since eGallon is the star of the show, let’s add the value to the eGallon price.
An Adjusted eGallon calculation
Taking into account the battery cost and the expenses involved in highway upkeep (taxes) we can derive an adjusted eGallon calculation. The result is not so one sided as the government’s calculations.
$1.09 – Government’s eGallon calculation for Texas (6/10/2013)
$1.97 – Per gallon EV battery cost (7 cents per mile x 28.2 miles per gallon) $0.38 – Taxes per gallon (Texas)
$3.44 Adjusted eGallon rate for Texas
This is compared to an average gas price in Texas of $3.37 per gallon.
It’s not all bad
All of this is not to dissuade the adoption of electric vehicles. It’s only meant provide a more realistic comparison between gas and electric. There are some things that can be done to tilt the equation back in favor of the electric vehicle.
Hopefully, battery technology will continue to improve resulting in longer lifespans and cheaper replacement costs. Also, second life applications for used EV batteries such as local or grid level power storage in support of wind and solar energy may help the residual value of old car batteries. That would help improve the numbers in favor of the eGallon.
Also, the electricity costs used in the government’s calculations are only averages. There is a lot consumers can do, particularly in deregulated states like Texas and New York to reduce that cost. The simplest is by just shopping multiple electricity providers to find the cheapest providers and plans.
As ‘time of day’ pricing becomes more practical because of smart meters, many electric companies are offering innovative plans such as Free nights and weekends electricity plans. With such a plan an electric vehicle owner could theoretically charge their vehicle overnight at zero electricity costs.
Keep in mind, however, as with the aforementioned taxes, costs rarely just disappear. More often they are just shifted elsewhere. This is the case with most free nights electricity plans. The day time rates are often substantially higher with these plans than traditional electricity plans. This means that while you may top off your car battery for free at night, you will pay a lot more to brew your morning coffee and keep your refrigerator running.