Not so sustainable, after all?

Finally sold my car!

Yes, I was considering to buy an EV, as I discussed in the post “To EV or not to EV”. But, for the moment I just sold my car and will try to be “car-less person”. At the end of the day, using public transport, car-sharing (we now have car2go in Madrid and it works great) and the bike is clearly more sustainable than owning any vehicle. (Well, and also borrowing my wife’s car sometimes…)

Parte trasera coche fino

But: I sold it. Which means my 15-year-old diesel guzzling 7-series BMW will still be consuming +15 l/100 km and emitting lots of particles and CO2 pollution. Depending on the distance the new owner will drive, it might be more ecological than him buying a new, more efficient, one. That’s because of increased asset utilization and vehicle construction sunken emissions. However, it might be that the most ecological and sustainable would be  Sigue leyendo

The grid as an emergency supply?

It’s official. Finally Spain has the most toll-intensive consumer power generation (what is called self-consumption) law in the world. The so-called “sun tax” is in place.

It is important to understand the worries of the regulator here;

Given the high fixed costs of the system, further reductions of electricity demand (as with self-consumption) increase the price of energy in a Grid independence cycle. The goal of increasing the toll on self-consumption is to ensure the system costs are covered, delay the implementation of self-consumption (starting in the islands and small systems), delay consumer energy storage (in fact it is also a “battery tax”) and (try to) avoid further political problems. Of course, it is not the best solution, academics and regulatory experts agree that politically fixed costs that have to be paid by all citizens shouldn’t be in the tariff but evenly paid from the nation’s bugdet (like the extra-costs for electricity in the islands).

Image by Cancia Leirissa on

“Grid Emergency Exit”                                                       Image by Cancia Leirissa on

What are the consequences? Rising prices, and the fact that fixed costs (for the contracted power) are surging, push the active consumer to look for the following solutions:

Sigue leyendo

Take the panel with you

Solar Panels are getting cheaper every day, so this idea might convince you less today than it could have some time ago…

Anyway, suppose you have bought yourself one 300 W solar panel for your flat. In fact you found a smart orientation that covers your “base load” for the fridge and all the stand-by consumption and also lowers your consumption once you arrive home. It happens you have a e-bike that is prepared for you to plug your panel, for your daily commuting, keeping your battery fine or even charging while you are working. Additionally, you own an Electric Vehicle. During the week-ends, you can dock your panel for the journey and lower your consumption. And it happens that you are as wealthy as to have a second house in the forest, which is off-grid, so you use the battery of the Electric Vehicle for your consumption and you also plug your panel when you arrive.

Panel cycle

This is just an example of maximizing the asset utilization of a panel, for house self-consumption in two locations, and also for mobility. This will not be the case for most people, of course. Besides, regulatory frameworks may promote the use of the panel to feed the grid when it would be underused only for self-consumption and could be connected elsewhere for other purposes. Anyhow, the point of having portable generation opens more possibilities for generating one’s own energy, in this case at home and also for transportation. It is also an application for extending the access to electricity in developing countries.

In fact, if a person consumes (as it is the case in Spain) 3487 kWh/year of electricity and 9908 kWh of total energy at the home, together with 12000 km/year of driving, which can be calculated as 2400 kWh (with an EV doing 20 kWh/100 km) it makes a total of 12308 kWh. In order to source this with solar PV, he would need approximately 6 kW of solar panels working 2000 equivalent hours. These 20 solar panels he cannot take around with him that easily. For the moment…

P.S.: Allow me to include the crowded house video as the song I thought about while writing…

DG extends asset life – PV Grid

The results from PV Grid study initial report were presented in Madrid this week (organized on the 3rd July by @UNEFotvoltaica) and there was some interesting discussion on Solar PV integration.

One of the issues presented by the distributors (Enel, Fenosa and Iberdrola) were the inverted power flows in substations and the difficulties to control voltage when distributed PV reaches certain penetration. This was specially the case for Enel Distribution, as they presented an example in Puglia of reverted power flow from +10 MW to -30 MW, consequence of distributed solar. In my opinion, although having much more distributed PV than spanish distributors (15,9 GW Vs 4,3 GW), was not as “worried”.

The issue I want to highlight here is actually the increase in PV penetration in distribution has the effect of reducing the load of distribution transformers, specially in the hottest moments, therefore reducing insulaton degradation (see IEC Thermal index and halving interval in IEC 60216). This can actually increase the life of these assets, benefitting the distribution company.

PV protecting trafo

It’s true that when power flows become reversed, and higher than normal consumption load, the effect is reduced lifetime, but up to this “reverted-equivalent-load” point it is of interest to the distributor to have additional distributed generation. Moreover, where losses influence the distributor’s regulated income, having enough PV to reach a load-consumption zero-sum as much time as possible during the day is in it’s economic interest (as in the following graph).

Load change with DG increase

In my opinion, distributors should set distributed generation targets per area in order to reduce their substation loads and increase their assets lifetime. Not too much intelligence (no smart grid hard/software)  is required to manage this, just setting the best case generation in the distribution, and promoting/accepting connection points up to the most appropriate to their network.