Direct Current for Zero Energy - Edison was Right!

"You see, we should make use of the forces of nature and should obtain all our power in this way. Sunshine is a form of energy, wind and sea currents are manifestations of this energy. Do we make use of them? Oh no! We burn forests and coal, like tenants burning down our front door for heating. We live like wild settlers and not as though these resources belong to us."

                                                         Thomas A. Edison, 1916

With those epic words, over 100 years ago, Thomas Edison predicted the environmental opportunities that we continue to fight for today in our energy – driven lifestyles. 

I was fascinated with the announcement that Microsoft was teaming up with Planet Labs and the Nature Conservancy to create Global Renewables Watch a satellite-based type of mapping system documenting the use of solar and wind renewable energy around the globe.  

This will be quite a leap toward accounting for the amount of energy we receive coming from non-traditional zero carbon energy sources. However, I always worry that we are only getting half the picture when we focus on renewable energy for powering our world. This is because when we only focus on renewables, we miss the valuable role played on the other side of the energy – demand equation, that of energy efficiency. In fact, most modern facilities, these days, cannot come close to achieving zero net energy without reducing energy use by at least 50% and typically many times more than that because of the extreme energy intensity of our lives today. 

That is why I always recommend an integrated approach to zero energy design, that factors extreme energy efficiency with wise and efficient use of onsite renewable energy. It is quite possible with modern lighting and motor technology accompanied with high insulation to achieve 50% energy reduction in a facility. But usually that is not enough to achieve zero energy.

However, when I speak of wise on-site use of renewable energy I am reminded of Thomas Edison yet again. For in the initial period around the formulations of the electric grid, Edison was a strong proponent of a direct-current based electric system rather than the alternating current championed by his rival, George Westinghouse, that we have today. One of the main reasons, was electrical efficiency.  Go watch the movie "The Current War" and you will understand.

Although alternating current (AC) was useful for transforming electricity from low voltage to high voltage for transmission making alternating current more practical for traditional transformers and motors, new electronic circuits today, make much of that obsolete, yet our system still relies on AC and we pay an electrical efficiency penalty. Just how much of a penalty do we pay?

Modern lighting systems, data processing centers and electronic (inverter-driven) motors for air conditioning operate naturally off of direct current (DC). Yet to operate them on AC circuits we must rectify the AC to DC, costing us as much as 15% in energy lost to heat in the transformation. Modern photovoltaic solar modules and the battery systems that provide backup power operate naturally in DC mode, but to connect them into the modern electric grid requires the use of inverters to transform the DC into AC. This costs as much as an additional 15% in energy lost to heat in the transformation process. 

Therefore, when you use LED lighting, inverter-driven motors and data processing servers off a solar system with battery and employ the normal inverter transformation on the solar DC to AC and then back again to DC for the loads, we lose as much as 30% in efficiency. This 30% penalty means that just powering anything off of solar in the AC world requires 1.3 MW of solar for every 1 MW of load. However, if we could not only integrate energy efficiency of 50% in with a DC to DC operation for the loads we could see a solar system that is potentially reduced by 65% to provide the same light and power for a facility as the standard AC-based solar that will be mapped in the new Global Renewables Watch system. 

Imagine that we now accept that Thomas Edison was right, that we need to focus our energy development around renewables, particularly solar, and that we operate our electric loads in an integrated energy-efficient and DC to DC basis, then we would more likely achieve out net zero goals while reducing the cost of solar and battery investment by two thirds. How much more could we show on the Global Renewables Watch System, if savings were increased from 50% to 65% while costs for solar and battery were reduced by 65%?