If you have several charts on one page, and they take a long time to load, you could consider showing them in HTML iframes. Iframes load asynchronously, using several active connections to the server at the same time. For example, your article could include iframes like this:
<h2>Please wait for the charts to load</h2>
<iframe src="http://mysite.com/index.php?view=article&id=96&tmpl=component"
style="width:100%; height:500px;"></iframe>
<iframe src="http://mysite.com/index.php?view=article&id=97&tmpl=component"
style="width:100%; height:500px;"></iframe>The tmpl=component parameter tells Joomla to return the component output (i.e. in this case, the article) without the rest of the page content.
To avoid having to create a separate article for each chart, you could use the Variable Chart ID as described above. Notice that in the first example we loaded two different articles (96 and 97). Here we are re-using the same article (96), and adding the chart_id variable:
<h2>Please wait for the charts to load</h2>
<iframe src="http://mysite.com/index.php?view=article&id=96&tmpl=component
&chart_id=68" style="width:100%; height:500px;"></iframe>
<iframe src="http://mysite.com/index.php?view=article&id=96&tmpl=component
&chart_id=69" style="width:100%; height:500px;"></iframe>