Typescript renderer import fails

dataset.ts

export class Dataset {
  name:string
  data: Data[]
  constructor(name: string) {
    this.data = new Data[];
  }
}

export class Data {
  time: Date
  value: number
  constructor(time: Date, value: number) {
    this.time = time;
    this.value = value;
  }
}

renderer.ts

const e = require("electron");
//import {Dataset, Data} from "./dataset"; // Error, Uncaught ReferenceError: exports is not defined
const ds = require("./dataset"); // works but cannot access classes

e.ipcRenderer.on("send-data", (data) => {
  let dataset = <ds.Dataset> data; // Error, cannot find namespace ds
  for (let d of dataset.data) {
    console.log("time: " + d.time + " value: " + d.value);
  }
});

server.ts

import dataset = require("./dataset");
import {ipcMain} from "electron";

function generateDataset(): Dataset {
  let ds = new Dataset("testdata");
  for (let i=0; i<100; i++) {
    let d = new Data(new Date(), i);
    ds.data.push(d);
  }
  ipcMain.sender.send("send-data", ds);                     
}

tsconfig.json

{
    "compilerOptions": {
        "outDir": "./built",
        "allowJs": true,
        "target": "es5",
        "moduleResolution": "node",
        "module": "commonjs",
        "sourceMap": true
    },
    "include": [
        "./src/**/*"
    ]
}