You need to do this:
1. Load the module (main.php):
'modules'=>array(
'shop',)
2. autoloading model and component classes of the modules:
'application.modules.shop.models.*',
'application.modules.shop.components.*',
3. You will need to pass the model and others necessary data to the view (if required):
$mymodel = new NewModel;
$data['someData'] = 'Data';
echo $this->renderPartial('shop.views.products.addToCart', array('model'=>$mymodel,'data'=>$data));
I have same issue and I soled in this way in my application and its working.