show panel when button is pressed

You have a typo in your code, the attribute you need is widgetVar:

<p:commandButton value="Search" ajax="false"
    actionListener="#{myBean.searchPatients}" onclick="panelwv.show();">
</p:commandButton>
<p:panel widgetVar="panelwv" visible="false" closable="true" toggleable="true"/>

If you don't want to render your panel at all you should consider using the rendered attribute of the component.