Magento - Initialize an (empty) cart, generate shipping rates

somewhere.php

    /**
     * Initialize an (empty) cart
     */
    protected function initCart()
    {
        if (!$this->cart->getQuote()->getId()) {
            $this->cart->getQuote()->getShippingAddress()
                ->setCountryId('DE')
                ->setCollectShippingRates(true)
                ->collectShippingRates();
            $this->cart->save();
        }
    }