Regarding Eriko Arita's May 14 article, "": I find the comments of Tetsunari Iida (executive director of the Institute for Sustainable Energy Policies) very interesting, but I have the following questions:

(1) When Iida says "Japan should target supplying 100 percent of power by renewable energy sources in 2050," does he mean 100 percent of what we have today or 100 percent of what we'll use in 2050—which might be 50 percent, 30 percent, etc. of what we use today. I don't mind if it's 10 percent, but it should be spelled out.

(2) Are we assuming that the whole energy system will create enough energy to make it possible to remanufacture the same equipment, such as solar panels, batteries and related items, and still provide society with substantial net energy?

I assume that this is what is meant. If not, it means that we might be producing 100 percent of power in 2050, but as the equipment ages and breaks down, we might be able to generate, say, only 20 percent of that amount of energy in 2080 or 2090. That would still be "100 percent" of the power used at that time.

If the answer to No. 2 is "no" or "don't know," then the power we would be generating in the 22nd century might be almost nothing compared to what we are generating now.

In that case, renewable energy would amount to only a transitional energy source between today's society and economy and the society and economy of the 22nd century—about which we can predict very little except that it is likely to look like Japan's Edo Period (1603-1868).

Few people seem to have realized this, certainly not Iida, who appears to think that the delivery of 100 percent of power by renewable energy sources in 2050 can continue for an indeterminate period into the future. I would be very happy to find out what Iida thinks about these questions.

The opinions expressed in this letter to the editor are the writer's own and do not necessarily reflect the policies of The Japan Times.

tony boys