So I bought Japanese ELM seed to grow my own bonsai. The thing is, I read everywhere that it need a lot of sun, especially in the morning. But where I live, I the sun doesn't reach the window until late afternoon and almost the same if I put it outside in the morning...
Will my bonsai be happy if I use an artificial light to replace the sun? And what are your recommendation for such use case?
It depends on the light. Normal household light is very very wreak for plants. A test: turn on the light at noon, and you will not find differences on your room, and from sun you will have only indirect light.
Many (illegal) Cannabis cultivation uses artificial light, but much more powerful, and so usually utility bill (or fire) cause the indoor cultivation to be uncovered).
So: possible, but not practical.
You don't say where about in the world you are, but most commonly Chinese elm is an outdoor plant (especially in the summer. If you are in a fairly mild climate then bringing inside or some decent frost protection outside should be taken.
Some good general advice on this bonsai is available Here.
In terms of artifical light, that really depends on your budget. Most commonly some form of metal halide light is used as grow lights, these however are costly to buy and also costly to run - usually burning 400w of electric per hour.
There are cheaper alternatives, there have been some good developments in LED lighting rigs, but you need to make sure that the set up is providing the right spectrum of lighting (usually a combination of red, blue and a couple of UVs for good measure. Again you will find that there are some cheap ones available (can't comment of their usefulness) and more expensive ones that have been shown in tests to yield good results. But that does come at a cost, although the cost of running them are far lower.
One other thing I would mention, when reading into this myself a while ago, I came across this Article where the guy used normal strip lighting placed fairly close to the trees.
I would be inclined to stick it on your best window ledge / spot in the yard for a while and see how mother nature gets on. Then if it seems to be struggling for light, try out some of the cheaper options as suplimentary lighting.
It's all about lumens when using indoor lights. Doesn't matter what type of lights leds, hids, cfls, or regulars florescent. Best would be 75 watts of hid like high pressure sodium, now these can be expensive and get very hot but they give off lumens that are similar to the summer sun (lower lumens but still 75-100watts). The most cost effective would be 65-75 watt CFL in a good reflector (flat white is the best for reflection. The other thing you will have to consider is putting your lights on a timer no more than 14 hrs of light a day. Also the air around the plant needs to be circulated constantly (a small fan will do the trick). Last thing is temp and humidity I don't know much about bonsai but I would find out what type of temp and humidity they like.
