Enbala Blog

I recently reviewed an EPRI document that discussed storage, and by far the largest size storage systems were pumped storage plants.  I wondered why they did not include hydro (non-pumped) storage, as this form of storage is far larger than any other form of storage that is available on the grid now.

Parts of North America, but sadly not all of it, are blessed with mountainous territory that has many rivers and streams that run downhill, and many of these have been harnessed for electricity production. While not specifically intended as storage plants when built, the value of their storage may well turn out to be larger than the value of the electricity that they may produce.

Consider a hydro dam that is 35 M in height with a reservoir that is 10 km². Discharging the top 1 M of water through a generating station (90% efficient) would release almost 840 MWh of stored energy. This is a small hydro plant, with a small reservoir behind it, yet the storage is almost 840 MWh/M of depth that is drawn from the forebay.  That is in addition to the electrical energy generated for use.

So how does a utility that has no pumps manage to store and return energy?  The process is both simple and efficient.   

There is no doubt that we are facing real problems with climate, fossil fuels and carbon emissions, but as we look to solve these problems, I think that we need to look carefully at the underlying facts, rather than focusing (as some do) on the short-term elimination of fossil fuel.

1. The biggest sources of emissions in the US are the generation of electricity from coal and transportation-related emissions (60% of which is for personal transportation). These two sources are responsible for more than 2/3 of total emissions.  Canada is only slightly better, in that its electric system generates almost 60% of total energy with hydro, and nuclear is a large contributor to clean electricity as well.  Canada’s petroleum industry ranks second, behind transportation.
2. Electricity provides less than 20% of total energy, and the remainder is almost all fossil fuel. The average person gets fuel in three forms: electricity, natural gas and transportation fuel (gasoline or diesel fuel).  Any major reduction in the direct delivery of fossil fuel will be expected to be replaced with electricity, and that may be a big challenge, given the fact that the electric grid at present delivers only about 20% of the total energy.
3. Many people seem to think that if they can convert their current electricity use to solar energy, the problem will be solved. They tend to forget, however, about heating and transportation fuel. In most cases, the fossil fuel energy is far larger than the electrical energy delivered.
4. I keep hearing that the problem is someone else’s fault – blame India, China, the oil industry or the government. We all need to look in the mirror – and recognize who the big users are.  The fact is that North Americans are among the largest users of energy per capita in the world.  As “Pogo” would have said, “We have seen the enemy, and it is us!”

There are two areas to look at: the supply of energy and the use of energy.

Utilities and regulators evaluate grid modernization initiatives using economic paradigms. They determine if investments at the grid edge are cost effective relative to investments made in traditional generation, transmission and distribution assets. The Intergovernmental Panel on Climate Change (IPCC) recently published a special report titled ‘Global Warming of 1.5°C’, with an accompanying Summary for Policymakers. The Summary stated that if global warming continues at its current rate, we will likely reach a 1.5°C increase in global mean surface temperature (GMST) compared to pre-industrial levels between the years 2030 and 2052. The Report and Summary provided a comparison of outcomes we can expect if GMST increases to 1.5°C versus 2.0°C. It also presented solutions to support limiting global warming to the smaller value.