Oven – Are there any 27″ residential ovens that can accomodate a 3/4 sheet pan

The forced movement (convection) of the hot air by fans is what improves the cooking in a convection oven. The beautiful part is that it allows you to cook on ANY or EVERY single rack in your oven. Here are the adjustments you'll need to make:

For baked goods you typically drop the temperature by 25°F (10°C). If the recipe says to bake at 350°F then you'd bake at 325°F in a convection oven. This is most important in baked goods so that the interior has a chance to cook through before the exterior is overcooked or burnt.

You also need to decrease the baking time by 10-15 PERCENT. To make it easier to determine when to check, I usually suggest checking the item about 5-10 minutes earlier than the shorter time indicated in the recipe. If a recipe says bake 25-30 minutes, then check it at about 20 minutes. It may need a bit more time but you'll be pretty close.

When roasting meats and vegetables you can use the above method OR you can leave it at the regular temperature and then cook for 25-30 PERCENT less time.

In the instance of method #1 for meat you'll get less shrinkage and less chance of possibly drying it out.

In the instance of method #2 for meat, it will cook quicker and get better browning and therefore a bit more flavor.

A third option to take advantage of both methods is to cook it at the reduced temperature for most of the time but then turn it up 25-50°F for the last 20-30 minutes of cooking to improve the browning.

I have not heard of any machine of that nature, and I try to keep up with an assortment of home beer brewing sources. If anyone would have come up with something, it would probably be brewers, since we tend to use large amounts of live yeast. About the most advanced thing I have heard of is storing wort in Nalgene bottles after boiling and using that for a starter. I can't think of an analog for sourdough that would be safe and keep the starter maintained with a good flavor. Pro brewers or bakers may have a tool that I'm unaware of, though.

I'm sure you could come up with some sort of Rube Goldberg machine to feed your starter, but really, it's like taking care of any living thing. You have to water and feed plants, animals, and yeast cultures. It's a small amount of work, too, really. Add water, flour, maybe some sugar, and stir. You might want to stick with non-sourdough breads if you can't make that kind of time investment.