Andy's Mind

A blog post that claims a 200×200 miles square collects enough solar energy to power all of humanity did create quite a lot of buzz on Twitter recently. I decided to check whether this is indeed true.

I started with finding out how much energy we really get from our nearest star – the Sun. It turns out there is a number known as the solar constant which describes exactly this and it was measured to be 1368 watts per square meter (W/m²).

200×200 miles is 40,000 square miles, or 103,684 square kilometeres, about 5 times the size of Wales. If we compute the potential power using the solar constant mentioned above we get 141.8 TW (tera watts) from this area. The total energy consumption of the world is estimated to be 15 TW (tera watts) – so far so good.

However, the solar constant is the energy we get from the Sun as measured in the orbit above the atmosphere. As long as we don’t consider energy collecting satellites we have to compute further. At ground level not only absorption and reflection by the atmosphere has to be taken into account, but also the fact that due to Earth’s rotation any given point on its surface is in the dark (not getting any energy) roughly half of the time.

The number we get when we factor all of this in is 342 watts per square meter. With this our 200×200 miles square produces 35.46 TW (tera watts). But this still doesn’t take into account the weather and the variation of solar irradiation related to latitude. Most of the current “developed world” is in the areas north and south of tropics, getting less sunlight. Because of this we can’t assume it will make sense to put all solar panels at the equator. And even there cloudy days happen.

I therefore assume solar generation would occur mostly in the southern regions of the “developed world” and base calculations on this. Different values are published re. irradiation on the ground in those regions. I decided to assume optimistically that what really reaches the ground is on average 275 watts per square meter. (source, source)

But this is just a potential energy – next problem is how effectively we can convert it into something that is useful for us, like electricity. Part of this is that the numbers above describe total energy of radiation coming from the sun, which is distributed along the spectrum (see how), not all of which can be changed into electricity. The other part is the technology we have at our disposal and its limitations. Right now generally available photovoltaic cells operate at 30% efficiency, some experimental systems exist that can get up to almost 40%.

If we now take also this into account a 200×200 square covered with generally available cells would produce 8.554 TW, if we could get Fraunhofer’s cells working at 40% in quantity we would get 11.41 TW.

That means we would need just a bit more than a 200×200 miles square covered (1.31464 more to be exact) with Frauhofer’s high yield cells to satisfy world’s demand at 15 TW. In other words the area needed would be 52 586 square miles – or 229×229 miles square: about twice the size of lake Victoria.

Now, I wanted to check my computations to see if they really add up (this is where I discovered an error in my original post). I looked at solar panels available on the market and computed how much power would the give if they were used to cover a 200×200 miles square.

Let’s take BP Solar‘s BP 3125, to which I was able to get the technical spec sheet [PDF]. According to it this panel produces 125 W of power from 0.876 square meters of cells (36 square cells). That means it generates 109.51 W / m2. If we were to cover our 200×200 miles square with those panels we would get 11.355 TW.

Of course this panel generates this amount of power only if exposed directly to sunlight, which means in reality such an array would produce less power due to Earth’s rotation (it would spend some of the time in the dark) and weather fluctuations. However, amazingly the computations above confirm we would need just a tiny part of the Earth’s surface to produce all the energy we need without any kind of emissions (except those made when making the panels and soldering them together).

The interesting question is then: why are we not doing it?

One frequently mentioned problem is the price of the panels. The cost per installed watt is estimated between $7.5 and $9.5 (source). Let’s assume it at $8 – that would mean 120 US$ trillion to replace 15 TW of power we need. This is almost 15 times the current official US national debt. Even at the current levels of US$ loss of value it is still a huge price tag.

However, no one would expect US to pay for all of it (even though US has been consuming most of oil and is consuming most of the energy). If we spread it amongst all industrialized nations of the globe it should be doable.

Another problem could be availability of raw materials and energy needed to produce required quantities of those cells in the first place. But this a question for a separate different article.

This article existed here for a couple of days in a completely different version based on computations which were based on an error. Interestingly, no one noticed until I started to check them again by computing backwards – that is by taking a real, available solar panel and computing how many watts of energy from square meter it can deliver. Sorry for any confusion caused.

Sales is understanding and satisfying clients’ needs, not pushing a product or solution onto them. Agile’s contribution is bringing back the understanding of the fact that what is the clients’ true need in software industry is, well, software.

I have started a videocast with a friend – and manager of a competing software company – Paul Klipp. We have been meeting and discussing agile software development, web applications & related stuff for some time and recently I realized we could turn this into a podcast. Paul has one of those neat Flip Mino HD cams and what was to be a podcast has turned into a videocast. So now you can listen to us discussing those topics bi-weekly under “Scrum for Success” (also available on iTunes).

The last episode covers the FOWA conference we both attended that I have blogged about last week.

On Friday I attended the Future Of Web Apps in Dublin (an event we sponsored). Here are the thoughts I brought back home with me.

First, it was hard not to notice the contrast between this conference and the world outside. Ireland is getting hit hard by the crisis and it shows. Taxi drivers were protesting the day we arrived and those that drove us around explained why: they are squeezed hard because demand for their services plummeted and supply skyrocketed as people laid off elsewhere try to earn a living turning their cars into taxis. Everywhere we went we have seen other signs of the crisis – like 1 Euro burgers advertised at McDonald’s. Walking the streets in Dublin you could smell the stale air from the burst bubble.

Enter the conference (ironically hosted in a trade unions building) and you are in a different world. The optimism was maybe not as exuberant as just two years ago, but still defiantly present. That is good – because we’ll all need liberal doses of optimism in the coming months and years. However, an event like this could have been a great moment to discuss how this industry should prepare to weather this coming storm – or even profit from it.

And prepare it should. The fact is that with angel investors disappearing and VCs getting tougher the (all too frequent) usual path to stardom and riches – develop an app, usually free for the end users, sell most of your company to the VCs, who will float it on the stock market, which will allow you to profit immensely from the 10% stake VCs left you with leaving the task of figuring out how to make your app profitable to someone else – is gone for good. And as more and more people get laid off (unemployment in Ireland is officially reaching 10%, so it is in the US) things like yet another social network won’t be high on their priorities.

But that just means only really good and useful ideas, applications people would like to pay for as users, things that will really help people (like, say, innovative job sites) will make it. I waited for the reality outside the conference room to be discussed – and I was sure I will wait in vain when finally at the very end David Heinemeier Hansson took the stage and told the audience few words of truth.

He told them, that days of counting on VCs to give you money for your cool but utterly useless idea are over. That you have to provide valuable service to users that you yourself would be willing to pay for. That what you are doing is a business for God’s sake and you should think of it as such. That you have to contribute valuable stuff to the community and world at large to earn recognition and fame – and it won’t come fast. That you have to believe in your idea no matter what others will tell you. And that you have to work hard and persevere in face of difficulties to get anywhere – which is probably something most people miss when they want to build “next Google”, “next Twitter” or “next Facebook” (When I hear people saying they will build “next” something I roll my eyes).

To all this I’d just add: and even with all of this you can still fail. Brace for it.

That talk was for me one of the highlights of this event. I have never heard Hansson speak before and I was really surprised that he clearly was a guy who did not forget that what got him where he is now was steadfast hard work.

In an event like this many of those attending are wannabes that want to be as rich and successful as those on the stage. Good that someone with a cult status like Hansson reminded them it is not all rosy and cool – but that hard work and overcoming difficulty is how to get anywhere.

Another great talk on FOWA Dublin was exactly aimed at those who follow the success stories too closely – especially design their apps to mimic some other software. This may be a good idea, but usually isn’t and leads to boring software.

Eoghan McCabe and Des Traynor of Contrast were trying to transmit exactly this with their impressively smooth and dynamic presentation. I don’t like the UIs they shoved in their slides – I prefer clean, minimalistic design, with no big graphics, no animations, no Flash etc. – but I think FOWA audience benefited from seeing examples of doing thing different. And from the Eoghan’s & Des’ general message: question conventions, question the “standard way” of doing things, question “design standards”, question them all the time.

But “question” doesn’t mean “throw away without considering”. If they are useful for you, follow them, but if you have a better idea – go for it.

Worth mentioning were also presentations on security (mainly for its delivery, as nothing really new was said) by Simon Willison and on accessibility by Robin Christopherson from AbilityNet (a very needed prospective on making the web open to those with disabilities, especially vision impairment).

Overall, this was a great day despite clear organizational shortcomings (crowded venue, rip-off bad coffee, flaky Wi-Fi etc. etc.). I’m sure Carsonified team will improve their events organizational side with time.

Other FOWA reviews:

• Dave Concannon’s very detailed review (will take half an hour to read 🙂 ),
• Peter Szinek’s laundry list of all organizational shortfalls.