Philosophers have long struggled to understand the notion of strong, as opposed to merely epistemic, emergence. One such genuinely metaphysical way would be to accept that the powers of wholes can under certain conditions be more than the sums of the powers of the parts. But what are the conditions under which emergence occurs and can we be sure that the suggested sense of emergence is strong enough? Arrangement of component powers will be crucial as the same powers differently arranged can constitute different resultant powers of their wholes. This shows that the composition of powers is not always linear and is non-mereological but it also shows an inadequacy of the vector model. On the plus side, it gives us a model for composition that is apt for technical artefacts and complex socio-technical systems. This version of emergentism also permits plausible cases of top-down causation given that causes and effects are simultaneous on the powers view.