יום שלישי, 26 ביולי 2011

Google Autonomous

Google Autonomous photoshop
Since Google has released some info of their autonomous vehicle experiments I've been eager to hear more about it.
I Think that starting with the private sector will not 'solve really big problems' as the article states.

I think that if Google presents this technology it must be implemented on large scale commercial architectures and not private vehicles, unless they are shared among users via car/time sharing (but that's another idea still far from beta testing...)


  • Mass transit system: Buses and rail systems that drive autonomous, never get tired or angry of other vehicle drivers, Here also the face recognition technology could come in handy if one can enter an automated bus and be recognized by the bus and be automatically reminded where my stop is, automatic ticketing etc'
  • Trucks / Semi : that suffer the worst from blind spots and work hours, here is the greatest opportunity to basically save lives if these mammoths were driven by precise robotics instead of an angry mob
  • FedEx and Mail systems that usually route daily could benefit the most
  • a good replacement for any Israeli driver (perhaps also for any Israeli politician too...)
I fear, although this technology is great, that it will very quickly be cracked, hacked and misused to send pizzas to classmates.

what do you think?

יום ראשון, 17 ביולי 2011

Solar Yield : Degradation and % Efficiency

Simple chart for Azimuth/Inclination and percent degraded yield from PV's used for sloped roofs: based local in Israel (A Google login required)
be sure to check out GreenTops site for more information

 Timelapse animation of a system we've installed in Elad, Israel, which shows the preperations, modeling and the last part shows how we evade the shadow. we've used a Trimble D-GPS to obtain ~1 cm resolution of the building and high walls that we had to take into consideration.
Your comments are most welcome
Do You wish to compare the yield of Your system to other systems? 

I'm working on a daily kWh per kWp installed on systems around Israel, you can monitor hundreds of systems using the JavaScript I'm working, the graph charts are in this link
there is about 10,000 kWp monitored daily that You can view how systems in Jerusalem yield differently than systems in the Golan, in cities or outside of them etc'.
if you like to be part of this statistics please inform me and I'll log Your system as well.
Thank You for reading this, Your comments are most welcome !

יום ראשון, 3 ביולי 2011

Practical Solar PV charts for installations

I've been asked a lot about how much degradation one should expect from having the wrong azimuth on a certain roof. also the inclination has an effect. I'll try to bring here the basic types I see common.

A roofs facing south are rare, but until we develop a tracking system that can use a standard roof tile installation, this is pretty much the degradation expected from a 22° inclination / Azimuth :


This Chart is only effecting 22° inclination roofs local at Israel. additional charts of different inclinations are located here.
The following interactive chart also shows expected degradation due to two variables: azimuth and 0°-25° inclination (geographical location Tel Aviv):

(to view a Google interactive chart you must log in your Google account)

When designing flat roof arrays, the row distance must allow the sunlight to be available for all of the array from 08:00-15:00 in winter at least and 07:30-17:00 in summer to enjoy the peak power of the array.
if the area doesn't allow it use these tips:

1. The build of the panel has some faults. when partially shadowed it may produce no energy at all. it seems that if it is shadowed on it's short side (for instance, a panel is standing) it will not generate energy. while if it is similarly shadowed on it's long side (a panel is lying) it will produce up to 66% energy even while shadowed.
Flat Panel with shadows drawing

2. it is smart to use technological improvements such as Tigo maximizer units but they are not cheap. sadly a lot of consumers think cheap and not think profitable, which can generate a lot of untapped energy. a large scale facility that isn't shadowed will think "why do I need this?" and forget about partial clouding or bird droppings that when one panel is down, the whole array goes down.

3. for flat roof installations, the following chart provides distances based on inclination of the panels (local iseael) and should provide maximum peak power at minimum distances, larger will be more effective:


(again, one must be logged in a Google account in order to view the interactive chart)
Be sure to check out GreenTops site for more info