Q1. It is because the lemon acts as a electrolyte.

Q2. Solar energy isn't harmful to nature, and has a never ending source of energy, the sun. But it is very pricey, and while building the solar energy system, it must have a place to be built, and it will harm nature in that process. I think the main point here is that, will it harm nature more in the building process, or will it benefit nature more when finished. But for now, the solar energy system is not fully grown. And I think it's too early to encourage the building of solar energy.

1. The paper clip and the penny is made out of zinc and cooper. Zinc loses electron easily and cooper doesn't lose electron not easily. But, if you just leave zinc and cooper alone, electrons don't move, so you need something to move the electrons, by using a thing that eletric current flows easily. This is called the electrolyte. And the lemon is the elctrolyte, because it contains acid so electric current flows easily in lemon, I think.

2. The good things about solar energy is that you don't have to worry about not using solar energy, because as we all know, sun is not something that can't last forever like things such as coal, oil etc... And it isn't also harmful to the nature. The sun is the nature itself so it doesn't pollute air, earth, or water so it's very good for the nature, and we don't have to worry about things like "Oh, there's not much solar energy left to use." But, there are some bad things about the solar energy, too. During cloudy days or rainy days, we can't use the solar energy since the solar energy comes from the sun. Also, it needs a lot of space to use the solar energy so not many people can use it easily. Even though using solar energy can be expensive for some people, it still has many good things about it, so I recommend that we should use the solar energy.