PostDoc position
Let's be more formal and call it a postdoctoral position, even if it says PostDoc on the ad.
Okay, and in the SECOND sentence of the essay you should give the reader the most powerful, persuasive sentence you can muster up. What is it? What is the unique, great idea that drives you? Can you adopt an idea that you know is meaningful to the organization with which you want the position?
I believe that I would be able to contribute to the field because my previous researches and experiences are tightly related to the topic.
You'll have to be more specific here. What do you mean? If you truly are ready to contribute to the field, you need to be able to express some unique idea instead of just generally saying you have research experience related to the topic. Give the reader something she can sink her teeth into. Give her a real concept/idea.
As you refine this, speak to their interests. What are their interests?
:-)
In the future, I would be very
much interested in examining the household electricity consumption ...